Polymer Chemistry Malcolm P. Stevens

Polymer Chemistry Malcolm P. Stevens
Professor of chemistry at the university of Hartfort OXFORD UNIVERSITY PRESS 3rd Ed.(1999) POLYMER CHEMISTRY

CONTENTS PART Ⅰ POLYMER STRUCTURE AND PROPERTIES Basic principles
Molecular weight and polymer solutions Chemical structure and polymer morphology Chemical structure and polymer properties Evaluation, characterization, and analysis of polymers POLYMER CHEMISTRY

CONTENTS PART Ⅱ VINYL POLYMERS 6. Free radical polymerization
Ionic polymerization Vinyl polymerization with complex coordination catalysts Reactions of vinyl polymers POLYMER CHEMISTRY

CONTENTS PART Ⅲ NONVINYL POLYMERS
10. Step-reaction and ring-opening polymerization 11. Polyethers, polysulfides, and related polymers Polyesters Polyamides and related polymers Phenol-, urea-, and melamine-formaldehyde polymers Heterocyclic polymers Inorganic and partially inorganic polymers Miscellaneous organic polymers Natural polymers POLYMER CHEMISTRY

Chapter 1. Basic principles
1.1 Introduction and Historical Development 1.2 Definitions 1.3 Polymerization Processes 1.4 Step-reaction Polymerization 1.5 Chain-reaction Polymerization 1.6 Step-reaction Addition and Chain-reaction Condensation 1.7 Nomenclature 1.8 Industrial Polymers 1.9 Polymer Recycling POLYMER CHEMISTRY

1.1 Introduction and Historical Development
Stone age → Bronze age → Iron age → Polymer age A. Development of civilization B. Application of polymeric materials ｏ PE milk bottles ｏ Polyamide bulletproof vests ｏ Polyurethane artificial heart ｏ Fluorinated phosphazene elastomer for arctic environments POLYMER CHEMISTRY

C. The purpose of this book
1. Property difference between polymer and low molecular weight compound 2. Chemistry of polymer synthesis 3. Chemistry of polymer modification POLYMER CHEMISTRY

D. Development of polymer chemistry
1833년 : Berzelius, the first use of terminology, polymer 1839년 : Synthesis of polystyrene 1860s : Poly(ethylene glycol), Poly(ethylene succinate) 1900s : Leo Baekeland, synthesis of phenol formaldehyde resin 1920s : Hermann staudinger Structure of polymer(long-chain molecules), Novel Prize(1953년) 1939년 : W.H. Carothers, Nylon synthesis (Du Pont) 1963년 : Ziegler-Natta, stereoregular polymerization 1974년 : Paul Flory, polymer solution property 1984년 : Bruce Merrifield, solid-phase protein process POLYMER CHEMISTRY

E. Examples of monomers and polymers
POLYMER CHEMISTRY

1.2 Definitions A. Acoording to the amount of repeating units
monomer : one unit oligomer : few polymer : many (poly – many, mer – part) telechelic polymer : polymer containing reactive end group (tele = far, chele = claw) telechelic oligomer : oligomer containing reactive end group macromer(=macro monomer) : monomer containing long chain POLYMER CHEMISTRY

1.2 Definitions B. DP : Degree of polymerization
The total number of repeating units contained terminal group C. The kinds of applied monomers B. DP : Degree of polymerization One kind : Homopolymer Two kinds : Copolymer Three kinds : Terpolymer POLYMER CHEMISTRY

D. Types of copolymer Homopolymer : -A-A-A-A-A-A-A-A-
Homopolymer : -A-A-A-A-A-A-A-A- Random copolymer : -A-B-B-A-B-A-A-B- Alternating copolymer : -A-B-A-B-A-B-A-B- Block copolymer : -A-A-A-A-B-B-B-B- Graft copolymer : -A-A-A-A-A-A-A-A- POLYMER CHEMISTRY B-B-B-B-B-

E. Representation of polymer types
linear (b) branch (c) network POLYMER CHEMISTRY

(or stepladder) polymer
F. Representation of polymer architectures (c)ladder polymer (b) comb polymer (a) star polymer (d) semi- ladder (or stepladder) polymer POLYMER CHEMISTRY

F. Representation of polymer architectures
(f) polycatenane (e) polyrotaxane (g) dendrimer POLYMER CHEMISTRY

G. Thermoplastic and thermoset (reaction to temperature)
Thermoplastic : Linear or branched polymer Thermoset : Network polymer POLYMER CHEMISTRY

1.3 Polymerization Processes
A. Classification of polymers to be suggested by Carothers Addition polymers : repeating units and monomers are same Condensation polymers : repeating units and monomers are not equal, to be split out small molecule POLYMER CHEMISTRY

Polyester from lactone (1.7) from ω-hydroxycarboxylic acid (1.8)
Other examples Polyester from lactone (1.7) & from ω-hydroxycarboxylic acid (1.8) (1.7) (1.8) POLYMER CHEMISTRY

2. Polyamide from lactam (1.9), and from ω-aminocarboxylic acid (1.10)
Other examples 2. Polyamide from lactam (1.9), and from ω-aminocarboxylic acid (1.10) (1.9) (1.10) POLYMER CHEMISTRY

3. Polyurethane from diisocyanate and dialcohol(1.11)
Other examples 3. Polyurethane from diisocyanate and dialcohol(1.11) and from diamine and bischloroformate(1.12): (1.11) (1.12) POLYMER CHEMISTRY

Other examples 4. Hydrocarbon polymer from ethylene (1.13), and from α,ω-dibromide (1.14) (1.13) (1.14) POLYMER CHEMISTRY

1.3 Polymerization Processes
B. Modern classification of polymerization according to polymerization mechanism Step growth polymerization : Polymers build up stepwise POLYMER CHEMISTRY Chain growth polymerization : Addition polymerization molecular weights increase successively, one by one monomer Ring-opening polymerization may be either step or chain reaction

1.4 Step-reaction Polymerization
A. Monomer to have difunctional group 1. One having both reactive functional groups in one molecule (1.8) (1.10) POLYMER CHEMISTRY

2. Other having two difunctional monomers
(1.11) (1.12) POLYMER CHEMISTRY

B. Reaction : Condensation reaction using functional group
Example - Polyesterification (1.3) (1.4) POLYMER CHEMISTRY

C. Carothers equation ( NO : number of molecules
P = NO N NO Or N = NO(1 P) ( NO : number of molecules N : total molecules after a given reaction period. NO – N : The amount reacted P : The reaction conversion ) ( DP is the average number of repeating units of all molecules present) DP = NO/N DP = 1 1 - P For example At 98% conversion POLYMER CHEMISTRY

(A) Unreacted monomer (B) 50% reacted, DP = 1.3 (C) 75% reacted, DP = 1.7 (D) 100% reacted, DP = 3

1.5 Chain-reaction Polymerization
A. Monomer : vinyl monomer χCH2=CH2 B. Reaction : Addition reaction initiated by active species C. Mechanism : Initiation R + CH2=CH2 → RCH2CH2 Propagation RCH2CH CH2=CH2 → RCH2CH2CH2CH2 . POLYMER CHEMISTRY

TABLE 1.1 Comparison of Step-Reaction and
Chain-Reaction Polymerization Step Reaction Chain Reaction Growth occurs throughout matrix by reaction between monomers, oligomers, and polymers DPa low to moderate Monomer consumed rapidly while molecular weight increases slowly No initiator needed; same reaction mechanism throughout No termination step; end groups still reactive Polymerization rate decreases steadily as functional groups consumed Growth occurs by successive addition of monomer units to limited number of growing chains DP can be very high Monomer consumed relatively slowly, but molecular weight increases rapidly Initiation and propagation mechanisms different Usually chain-terminating step involved Polymerizaion rate increases initially as initiator units generated; remains relatively constant until monomer depleted aDP, average degree of polymerization.

1.6 Step-reaction Addition and A. Step-reaction Addition.
Chain-reaction Condensation A. Step-reaction Addition. (1.15) POLYMER CHEMISTRY

1.6 Step-reaction Addition and Chain-reaction Condensation
B. Chain-reaction Condensation (1.16) POLYMER CHEMISTRY

1.7 Nomenclature A. Types of Nomenclature
a. Source name : to be based on names of corresponding monomer Polyethylene, Poly(vinyl chloride), Poly(ethylene oxide) b. IUPAC name : to be based on CRU, systematic name Poly(methylene), Poly(1-chloroethylene), Poly(oxyethylene) c. Functional group name : Acoording to name of functional group in the polymer backbone Polyamide, Polyester POLYMER CHEMISTRY

1.7 Nomenclature d. Trade name : The commercial names by manufacturer Teflon, Nylon e. Abbreviation name : PVC, PET f. Complex and Network polymer : Phenol-formaldehyde polymer g. Vinyl polymer : Polyolefin POLYMER CHEMISTRY

1.7.1 Vinyl polymers A. Vinyl polymers
a. Source name : Polystyrene, Poly(acrylic acid), Poly(α-methyl styrene), Poly(1-pentene) b. IUPAC name : Poly(1-phenylethylene), Poly(1-carboxylatoethylene) Poly(1-methyl-1-phenylethylene), Poly(1-propylethylene) Polystyrene Poly(acrylic acid) Poly(α-methylstyrene) Poly(1-pentene) POLYMER CHEMISTRY

1.7.1 Vinyl polymers B. Diene monomers 1,2-addition 1,4-addition
Source name : 1,2-Poly(1,3-butadiene) 1,4-Poly(1,3-butadiene) IUPAC name : Poly(1-vinylethylene) Poly(1-butene-1,4-diyl) cf) Table 1.2 POLYMER CHEMISTRY

1.7.2 Vinyl copolymer Systematic Concise
Poly[styrene-co-(methyl methacrylate)] Poly[styrene-alt-(methyl methacrylate)] Polystyrene-block-poly(methyl methacrylate) Polystyrene-graft-poly(methyl methacrylate) Concise Copoly(styrene/methyl methacrylate) Alt-copoly(styrene/methyl methacrylate) Block-copoly(styrene/methyl methacrylate) Graft-copoly(styrene/methyl methacrylate) POLYMER CHEMISTRY

1.7.3 Nonvinyl Polymers oxy 1-oxopropane-1,3-diyl ethylene
terephthaloyl POLYMER CHEMISTRY

* Representative Nomenclature of Nonvinyl Polymers
Monomer Polymer Source or IUPAC name structure repeating unit Common Name Poly(ethylene oxide) Poly(oxyethylene) Poly(ethylene glycol) Poly(oxyethylene) Poly(hexamethylene Poly(iminohexane- sebacamide) or Nylon6,10 1,6-diyliminosebacoyl) cf) Table 1.3 POLYMER CHEMISTRY

1.7.4 Nonvinyl copolymers a. Poly(ethylene terephthalate-co-ethylene isophthalate) b. Poly[(6-aminohexanoic acid)-co-(11-aminoundecanoic acid)] POLYMER CHEMISTRY

1.7.5 End Group α-Hydro-ω-hydroxypoly(oxyethylene) POLYMER CHEMISTRY

1.7.6 Abbreviations PVC Poly(vinyl chloride)
PVC Poly(vinyl chloride) HDPE High-density polyethylene LDPE Low-density polyethylene PET Poly(ethylene terephthalate) POLYMER CHEMISTRY

1.8 Industrial Polymers a. The world consumption of synthetic polymers
: 150 million metric tons per year. 1) Plastics : 56% 2) Fibers : 18% 3) Synthetic rubber : 11% 4) Coating and Adhesives : 15% b.Styrene-butadiene copolymer Synthetic rubber, PET Fiber (polyester) Latex paint Plastic (bottle) POLYMER CHEMISTRY

1.8.1 Plastics 1) Commodity plastics
LDPE, HDPE, PP, PVC, PS cf) Table 1.4 2) Engineering plastics Acetal, Polyamide, Polyamideimide, Polyarylate, Polybenzimidazole, etc. cf) Table 1.5 3) Thermosetting plastics Phenol-formaldehyde, Urea-formaldehyde, Unsaturated polyester, Epoxy, Melamine-formaldehyde cf) Table 1.6 4) Functional plastics Optics, Biomaterial, etc. POLYMER CHEMISTRY

TABLE 1.4 Commodity Plastic
Type Abbreviation Major Uses Low-density polyethylene High-density Polyethylene Polypropylene Poly(vinyl chloride) Polystyrene LDPE HDPE PP PVC PS Packaging film, wire and cable insulation, toys, flexible bottles housewares, coatings Bottles, drums, pipe, conduit, sheet, film, wire and cable insulation Automobile and appliance parts, furniture, cordage, webbing, carpeting, film packaging Construction, rigid pipe, flooring, wire and cable insulation, film and sheet Packaging (foam and film), foam insulation appliances, housewares, toys POLYMER CHEMISTRY

TABLE 1.5 Principal Engineering Plastics
Chapter Where Discussed Type Abbreviation C Acetala Polyamideb Polyamideimide Polyarylate Polybenzimidazole Poltcarbonate Polyeseterc Polyetheretherketone Polyetherimide Polyimide Poly(phenylene oxide) Poly(phenylene sulfide) Polysulfoned POM PAI PBI PC PEEK PEI PI PPO PPS 11 13 12 17 POLYMER CHEMISTRY

TABLE 1.6 Principal Thermosetting Plastics
Chapter Where Discussed Type Abbreviation Typical Uses Phenol-formaldehyde Urea-formaldehyde Unsaturated polyester Epoxy Melamine-formaldehyde PF UF UP - MF Electrical and electronic equipment, automobile parts, utensil handles, plywood adhesives, particle board binder Similar to PF polymer; also treatment of textiles, coatings Construction, automobile parts, boat hulls, marine accessories, corrosion-resistant ducting, pipe, tanks, etc., business equipment Protective coatings, adhesives, electrical and electronics applications, industrial flooring highway paving materials, composites Similar to UF polymers; decorative panels, counter and table tops, dinnerware 14 14 12 11 14

1.8.2 Fibers 1) Cellulosic : Acetate rayon, Viscose rayon
2) Noncellulosic : Polyester, Nylon(Nylon6,6, Nylon6, etc) Olefin (PP, Copolymer(PVC 85%+PAN and others 15%; vinyon)) 3) Acrylic : Contain at least 80% acrylonitrile (PAN 80% + PVC and others 20%) POLYMER CHEMISTRY

1.8.3 Rubber (Elastomers) 1) Natural rubber : cis-polyisoprene
2) Synthetic rubber : Styrene-butadiene, Polybutadiene, Ethylene-propylene(EPDM), Polychloroprene, Polyisoprene, Nitrile, Butyl, Silicone, Urethane 3) Thermoplastic elastomer : Styrene-butadiene block copolymer (SB or SBS) POLYMER CHEMISTRY

TABLE 1.7 Principal Synthetic Fibers
Type Cellulosic Acetate rayon Viscose rayon Noncellulosic Polyester Nylon Olefin Acrylic Description Cellulose acetate Regenerated cellulose Principally poly(ethylene terephthalate) Includes nylon 66, nylon 6, and a variety of other aliphatic and aromatic polyamides Includes polypropylene and copolymers of vinyl chloride, with lesser amounts of acrylonitrile, vinyl acetate, or vinylidene chloride (copolymers consisting of more than 85% vinyl chloride are called vinyon fibers) Contain at least 80% acrylonitrile; included are modacrylic fibers comprising acrylonitrile and about 20% vinyl chloride or vinylidene chloride

1.8.4 Coating and Adhesives 1) Coating :
Lacquer, Vanishes, Paint (Oil or Latex), Latex 2) Adhesives : Solvent based, Hot melt, Pressure sensitive, etc. Acrylate, Epoxy, Urethane, Cyanoacrylate POLYMER CHEMISTRY

TABLE 1.8 Principal Types of Synthetic Rubber
Styrene-butadiene Polybutadiene Ethylene- propylene Polychloroprene Polyisoprene Nitrile Butyl Silicone Urethane Description Copolymer of the two monomers in various proportions depending on properties desired; called SBR for styrene-butadiene rubber Consists almost entirely of the cis-1,4 polymer Often abbreviated EPDM for ethylene-propylene-diene monomer; made up principally of ethylene and propylene units with small amounts of a diene to provide unsaturation Principally the trans-1,4polymer, but also some cis-1,4 and 1,2 polymer; also known as neoprene rubber Mainly the cis-1,4 polymer; sometimes called “synthetic natural rubber” Copolymer of acrylonitrile and butadiene, mainly the latter Copolyner of isobutylene and isoprene, with only small amounts of the Latter Contains inorganic backbone of alternating oxygen and methylated silicon atoms; also called polysiloxane (Chap. 15) Elastomers prepared by linking polyethers through urethane groups (Chap. 13)

1.9 Polymer Recycling a. Durability of polymer property
1) Advantage : Good materials for use 2) Disadvantage : Environmental problem b. Treatment of waste polymer : Incinerate, Landfill, Recycling ex) Waste Tire : Paving materials Waste PET : To make monomer ( hydrolysis ) To make polyol ( glycolysis ) POLYMER CHEMISTRY

Letters Plastic Number TABLE 1.9 Plastics Recycling Codea PETEb
2 3 4 5 6 7 Letters PETEb HDPE V or PVC LDPE PP PS OTHER Plastic Poly(ethylene terephthalate) High-density polyethylene Poly(vinyl chloride) Low-density polyethylene Polypropylene Polystyrene Others or mixed plastics aAdopted by the Society of the Plastics lndustry (SPI). bPET is the more widely accepted abbreviation. POLYMER CHEMISTRY

Chapter 2. Molecular Weight and Polymer Solutions
2.1 Number average and weight average molecular weight 2.2 Polymer solutions 2.3 Measurement of number average molecular weight 2.4 Measurement of weight average molecular weight 2.5 Viscometry 2.6 Molecular weight distribution POLYMER CHEMISTRY

2.1 Number Average and Weight Average Molecular Weight
A. The molecular weight of polymers a. Some natural polymer (monodisperse) : All polymer molecules have same molecular weights. b. Synthetic polymers (polydisperse) : The molecular weights of polymers are distributed c. Mechanical properties are influenced by molecular weight much lower molecular weight ; poor mechanical property much higher molecular weight ; too tough to process optimum molecular weight ; for vinyl polymer 15, ,000 for polar functional group containing polymer (polyamide) POLYMER CHEMISTRY

B. Determination of molecular weight
Absolute method : mass spectrometry colligative property end group analysis light scattering ultracentrifugation. b. Relative method : solution viscosity c. Fractionation method : GPC POLYMER CHEMISTRY

C. Definition of average molecular weight
a. number average molecular weight ( Mn ) Mn= (colligative property and end group analysis) b. weight average molecular weight ( Mw) Mw= (light scattering)  i i Ni N M WiMi Wi POLYMER CHEMISTRY

c. z average molecular weight ( MZ )
MZ= (ultracentrifugation) d. general equation of average molecular weight : M = ( a=0 , Mn a=1 , Mw a=2 , Mz ) e. Mz > Mw > Mn C. Definition of average molecular weight NiMi3 NiMi2 NiMia+1 NiMia POLYMER CHEMISTRY

D. Polydispersity index : width of distribution
polydispersity index (PI) = Mw / Mn ≥ 1 POLYMER CHEMISTRY

E. Example of molecular weight calculation
a. 9 moles, molecular weight (Mw) = 30,000 5 moles, molecular weight ( Mw) = 50,000 (9 mol x 30,000 g/mol) + (5 mol x 50,000 g/mol) Mn= = 37,000 g/mol 9 mol + 5 mol 9 mol(30,000 g/mol)2 + 5 mol(50,000 g/mol)2 Mw = = 40,000 g/mol 9 mol(30,000 g/mol) + 5 mol(50,000 g/mol) POLYMER CHEMISTRY

E. Example of molecular weight calculation
b. 9 grams, molecular weight ( Mw ) = 30,000 5 grams, molecular weight ( Mw ) = 50,000 = 35,000 g/mol Mn = 9 g + 5 g (9 g/30,000 g/mol) + (5 g/50,000 g/mol) Mw = = 37,000 g/mol POLYMER CHEMISTRY

2.2 Polymer Solutions A. Process of polymer dissolution : two step
first step : the solvent diffuses into polymer masses to make a swollen polymer gel second step : swollen polymer gel breaks up to solution POLYMER CHEMISTRY

2.2 Polymer Solutions B. Thermodynamics of solubility :
Gibb's free energy relationship G =H - TS ΔG < 0 : spontaneously dissolve T and ΔS are always positive for dissolving process. Conditions to be negative ΔG, ΔH must be negative or smaller than TΔS. POLYMER CHEMISTRY

C. Solubility parameter : δ
Hmix=Vmix[( )1/2-( ) 1/2]212 ψ1, ψ2 = volume fraction ΔE1/V1, ΔE2/V2 = cohesive energy densities δ1, δ2 = solubility parameter δ1, δ2 = ( )1/2 Hmix= Vmix(δ1 – δ2)212 E = Hvap- RT δ1 = ( )1/2 if δ1= δ2, then Hmix= 0 V1 E1 V2 E2 V E V H vap - RT POLYMER CHEMISTRY

D. Small's and Hoy's G parameter
a. Small(designated G derived from Heat of vaporization, Table 2.1) δ = ( d : density , M : molecular weight of unit ) ex) polystyrene δ = = 9.0 b. Hoy(designated G based on vapor pressure measurement, Table 2.1) ex) polystyrene : dG M M 104 1.05( ) dG M 104 1.05[ (117.1)] = 9.3 POLYMER CHEMISTRY

E. Hydrodynamic volume of polymer molecules in solution.
to be depended on followings polymer-polymer interaction b. solvent-solvent interaction c. polymer-solvent interaction d. polymer structure ( branched or not ) e. brownian motion r = end-to-end distance s = radius of gyration Figure 2.1 Coil molecular shape r 2 = ro22 s2= so22  = (r2)1/2 (ro2)1/2 The greater the value of α, the ‘better’ the solvent α = 1, 'ideal' statistical coil.

2.2 Polymer Solutions F. theta(θ) temperature and theta(θ) solvent
The lowest temperature at which α=1 : theta(θ) temperature blink The solvent satisfied this condition : theta(θ) solvent point G. Flory-Fox equation : The relationship among hydrodynamic volumes, intrinsic viscosity and molecular weight [η] : intrinsic viscosity M : average molecular weight ψ : Flory constant (3×1024/mol) r : end-to-end distance [η] = (r2)3/2 M POLYMER CHEMISTRY

2.2 Polymer Solutions H. Mark-Howink-Sakurada equation
: The relationship between intrinsic viscosity and molecular weight [η] : intrinsic viscosity K , a : constant for specific polymer and solvent M : average molecular weight I. Important properties of polymer solution : solution viscosity a. paint spraying and brushing b. fiber spinning [η] = KMa POLYMER CHEMISTRY

2.3 Measurement of Number Average Molecular Weight
2.3.1 End-group Analysis A. Molecular weight limitation up to 50,000 B. End-group must have detectable species a. vinyl polymer : -CH=CH2 b. ester polymer : -COOH, -OH c. amide and urethane polymer : -NH2, -NCO d. radioactive isotopes or UV, IR, NMR detectable functional group POLYMER CHEMISTRY

2.3 Measurement of Number Average Molecular Weight
2 x 1000 x sample wt Mn = C. meq COOH + meq OH D. Requirement for end group analysis 1. The method cannot be applied to branched polymers. 2. In a linear polymer there are twice as many end of the chain and groups as polymer molecules. 3. If having different end group, the number of detected end group is average molecular weight. 4. End group analysis could be applied for polymerization mechanism identified E. High solution viscosity and low solubility : Mn = 5,000 ～ 10,000 POLYMER CHEMISTRY

FIGURE 2.2 Schematic representation of a membrane osmometer.

2.3.2 Membrane Osmometry A. According to van't Hoff equation limitation of : 50,000～2,000,000 The major error arises from low-molecular-weight species diffusing through the membrane. ( c  )C=0 = Mn RT + A2C FIGURE 2.3 Automatic membrane osmometer [Courtesy of Wescan Instruments, Inc.]

FIGURE 2.4. Plot of reduced osmotic pressure (/c) versus concentration (c).
Mn RT C Slope = A2 POLYMER CHEMISTRY

2.3.3 Cryoscopy and Ebulliometry
A. Freezing-point depression (Cryoscopy) Tf : freezing-point depression, C : the concentration in grams per cubic centimeter R : gas constant T : freezing point Hf: the latent heats of fusion A2 : second virial coefficient ( C Tf )C=0 = Hf Mn RT2 + A2C POLYMER CHEMISTRY

2.3.3 Cryoscopy and Ebulliometry
B. Boiling-point elevation (Ebulliometry) Tb : boiling point elevation H v : the latent heats of vaporization We use thermistor to major temperature. (1×10-4℃) limitation of Mn : below 20,000 ( C Tb )C=0 = HvMn RT2 + A2C POLYMER CHEMISTRY

2.3.4 Vapor Pressure Osmometry
The measuring vapor pressure difference of solvent and solution drops. λ : the heat of vaporization per gram of solvent m : molality limitation of Mn : below 25,000 Calibration curve is needed to obtain molecular weight of polymer sample Standard material : Benzil T = ( 100 RT2 )m POLYMER CHEMISTRY

2.3.5 Mass spectrometry A. Conventional mass spectrometer for low molecular-weight compound energy of electron beam : electron volts (eV) POLYMER CHEMISTRY

B. Modified mass spectrometer for synthetic polymer
a. matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) b. matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) c. soft ionization sampling : polymers are imbedded by UV laser absorbable organic compound containing Na and K. d. are calculated by using mass spectra. e. The price of this mass is much more than conventional mass. f. Up to = 400,000 for monodisperse polymers. POLYMER CHEMISTRY

FIGURE 2.5. MALDI mass spectrum of low-molecular-weight poly(methyl methacrylate).
POLYMER CHEMISTRY

2.3.6 Refractive Index Measurement
A. The linear relationship between refractive index and 1/Mn . B. The measurement of solution refractive index by refractometer. C. This method is for low molecular weight polymers. D. The advantage of the method is simplicity. POLYMER CHEMISTRY

2.4 Measurement of Weight Average Molecular Weight
2.4.1 Light Scattering A. The intensity of scattered light or turbidity(τ) is depend on following factors a. size b. concentration c. polarizability d. refractive index e. angle f. solvent and solute interaction g. wavelength of the incident light POLYMER CHEMISTRY

g. wavelength of the incident light
C : concentration no: refractive index of the solvent λ : wavelength of the incident light No : Avogadro's number dn/dc : specific refractive increment P() : function of the angle,θ A2 : second virial coefficient Zimm plot (after Bruno Zimm) : double extrapolation of concentration and angle to zero (Fig 2.6)  = HcMW 32 3 H = 4No No2(dn/dc)2  Hc = MP() 1 + 2A2C POLYMER CHEMISTRY

FIGURE 2.6. Zimm plot of light-scattering data.
sin2/2 + kc  Hc Mw 1 C=0 Experimental Extrapolated POLYMER CHEMISTRY

2.4.1 Light Scattering B. Light source
High pressure mercury lamp and laser light. C. Limitation of molecular weight( ) : 104～107 FIGURE 2.7. Schematic of a laser light-scattering photometer. POLYMER CHEMISTRY

2.4.2 Ultracentrifugation A. This technique is used
a. for protein rather than synthetic polymers. b. for determination of Mz B. Principles : under the centrifugal field, size of molecules are distributed perpendicularly axis of rotation. Distribution process is called sedimentation. POLYMER CHEMISTRY

2.5 Viscometry A. IUPAC suggested the terminology of solution viscosities as following. Relative viscosity :  : solution viscosity o: solvent viscosity t : flow time of solution t o: flow time of solvent Specific viscosity : Reduced viscosity : Inherent viscosity : Intrinsic viscosity : rel = o  = to t rel - 1 sp = o  - o = to t - to c rel = sp inh = In rel [] = ( )c=o=(ηinh)C = 0 POLYMER CHEMISTRY

FIGURE 2.8. Capillary viscometers : (A) Ubbelohde, and (B) Cannon-Fenske.
POLYMER CHEMISTRY

B. Mark-Houwink-Sakurada equation [η] = KMa log[η] = logK + alogMv
[η] = KMa log[η] = logK + alogMv (K, a : viscosity-Molecular weight constant, table2.3) Mv is closer to Mw than Mn Mw > Mv > Mn POLYMER CHEMISTRY

TABLE 2.3. Representative Viscosity-Molecular Weight Constantsa
Polymer Polystyrene (atactic)c Polyethylene (low pressure) Poly(vinyl chloride) Polybutadiene 98% cis-1,4, 2% 1,2 97% trans-1,4, 3% 1,2 Polyacrylonitrile Poly(methyl methacrylate-co-styrene) 30-70 mol% 71-29 mol% Poly(ethylene terephthalate) Nylon 66 Solvent Cyclohexane Cyclihexane Benzene Decalin Benzyl alcohol Cyclohexanone Toluene DMFg DMF 1-Chlorobutane M-Cresol Temperature, oC 35 d 50 25 135 155.4d 20 30 Molecular Weight Range  10-4 8-42e 4-137e 3-61f 3-100e 4-35e 7-13f 5-50f 5-16f 5-27e 3-100f 5-55e e f 1.4-5f ab 0.50 0.599 0.74 0.67 1.0 0.725 0.753 0.81 0.75 0.63 0.95 0.61 Kb 103 80 26.9 9.52 67.7 156 13.7 30.5 29.4 16.6 39.2 17.6 24.9 0.77 240 aValue taken from Ref. 4e. bSee text for explanation of these constants. cAtactic defined in Chapter 3. d temperature. eWeight average. fNumber average. gN,N-dimethylformamide. POLYMER CHEMISTRY

2.6 Molecular Weight Distribution
2.6.1 Gel Permeation Chromatography (GPC) A. GPC or SEC (size exclusion chromatography) a. GPC method is modified column chromatography. b. Packing material: Poly(styrene-co-divinylbezene), glass or silica bead swollen and porous surface. c. Detector : RI, UV, IR detector, light scattering detector d. Pumping and fraction collector system for elution. e. By using standard (monodisperse polystyrene), we can obtain Mn , Mw . POLYMER CHEMISTRY

FIGURE 2.9. Schematic representation of a gel permeation chromatograph.
POLYMER CHEMISTRY

Elution volume (Vr) (counts) Baseline Detector response
FIGURE Typical gel permeation chromatogram. Dotted lines represent volume “counts.” Elution volume (Vr) (counts) Baseline Detector response POLYMER CHEMISTRY

Heterograft copolyner Poly (methyl methacrylate) Poly (vinyl chloride)
FIGURE Universal calibration for gel permeation chromatography. THF, tetrahydrofuran. Log([η]M) 109 108 107 106 105           Polystyrene (linear) Polystyrene (comb) Polystyrene (star) Heterograft copolyner Poly (methyl methacrylate) Poly (vinyl chloride) Styrene-methyl methacrylate graft copolymer Poly (phenyl siloxane) (ladder) Polybutadiene            POLYMER CHEMISTRY Elution volume ()5 ml counts, THF solvent)

Retention volume (Vr) (counts) Molecular weight (M)
FIGURE Typical semilogarithmic calibration plot of molecular weight versus retention volume. Retention volume (Vr) (counts) 106 105 104 103 Molecular weight (M) POLYMER CHEMISTRY

)log( ) + ( )logM1 B. Universal calibration method
to be combined Mark-Houwink-Sakurada equation [η]1M1 = [η]2M2 logM2 = ( 1 + a2 1 )log( K2 K1 ) + ( 1 + a1 )logM1 POLYMER CHEMISTRY

2.6.2 Fractional Solution Soxhlet-type extraction by using mixed solvent. Reverse GPC : from low molecular weight fraction to high molecular weight fraction Inert beads are coated by polymer sample. POLYMER CHEMISTRY

2.6.3 Fractional Precipitation
Dilute polymer solution is precipitated by variable non-solvent mixture. Precipitate is decanted or filtered Reverse fractional solution : from high molecular weight fraction to low molecular fraction POLYMER CHEMISTRY

2.6.4. Thin-layer Chromatography (TLC)
Alumina- or silica gel coated plate. Low cost and simplicity. Preliminary screening of polymer samples or monitoring polymerization processes. POLYMER CHEMISTRY

Chapter 3. Chemical Structure and Polymer Morphology
3.1 Introduction 3.2 Molecular weight and intermolecular forces 3.3. The Amorphous State - Rheology 3.4 Glass Transition Temperature 3.5 Stereochemistry 3.6 Crystallinity 3.7 Liquid Crystallinity 3.8 Chemical Crosslinking 3.9 Physical Crosslinking. 3.10 Polymer Blends Chapter 3. Chemical Structure and Polymer Morphology POLYMER CHEMISTRY

3.1 Introduction heat and flame resistance.
A. The polymer properties for applications a. Plastic : toughness, durability, transparency, weather resistance, heat and flame resistance. b. Fiber : tensile strength, spinnability, dyeability. c. Rubber : resilience. POLYMER CHEMISTRY

3.1 Introduction B. Main subject of polymer chemistry :
The effect of chemical structure on polymer properties C. Type of polymer properties a. Mechanical properties b. Thermal properties c. Chemical properties d. Other physical properties

D. Polymer morphology : structure, arrangement, and physical form
a. Amorphous : lack of order among the molecules b. Crystalline or semicrystalline : regular orientation in the crystal lattice (not 100% of crystal for polymer) * intermolecular and intramolecular forces * stereochemistry, * chemical composition c. Network : crosslinked polymer chain d. Polymer blend : mixing polymers e. Others : liquid crystallinity. POLYMER CHEMISTRY

3.2 Molecular weight and intermolecular forces
A. Factors influencing mechanical property a. Molecular weight b. Chemical composition c. Intermolecular forces B. Intermolecular forces a. Hydrogen bond (eg., polyamide) : strong interaction b. Dipole-dipole interaction (eg., polyester) : strong interaction POLYMER CHEMISTRY 3.2 Molecular weight and intermolecular forces

FIGURE 3.1. Intermolecular forces in polar polymers : (a) dipole-dipole in a polyester;
(b) hydrogen bonding in a polyamide; and (c) ionic in a carboxyl-containing polymer. δ- δ+ (a) (b) (c)

3.2 Molecular weight and intermolecular forces
C. Example: Interaction depends on molecular weight a. Polyethylene (Mw=10,000) : Waxy solid, poor mechanical property b. Polyester and Nylon (Mw=10,000) : hard and brittle, good mechanical property D. Distance between molecules influences intermolecular forces and mechanical property a. Unstretched rubber band (long distance between molecules) : amorphous state, lower molecules, susceptible to attack by organic solvent b. Stretched rubber band (short distance between molecules) : crystalline state, higher modulus (2000 times), solvent resistance POLYMER CHEMISTRY

3.3. The Amorphous State - Rheology
A. Amorphous state: Characteristic of the solid state, but no crystallinity Solid amorphous: molecular motion이 제한적임 (very short range의 vibration과 rotation만 가능) Liquid amorphous: Segmental motion 가능 (conformational freedom존재) POLYMER CHEMISTRY

a. Molecular scale of amorphous state :
A. Amorphous state: Characteristic of the solid state, but no crystallinity a. Molecular scale of amorphous state : * for solid amorphous state, a bowl of cooked spaghetti (short range restricted vibrational and rotational motion) * for liquid amorphous state, can of worms (wriggling, jumping and rotational segmental motion) b. Rheology : Science of deformation and flow to be of more interest to engineer or physicist to be useful for designing processing machine cf) Chemist designs polymer molecular structure to be processed. POLYMER CHEMISTRY

B. Viscoelastic property of polymer
a. Die swelling of molten polymer PRESSURE Die swell Molten polymer FIGURE 3.2. Schematic representation of polymer flow through a die orifice. b. Time dependent bouncing and flowing of Silly Putty. POLYMER CHEMISTRY

. C. Shear a. Shear stress (τ) :
 = (tangential stress) (F: force, A: area) b. Shear strain : amount of deformation c. Shear modulus G=τ/γ : the ratio of shear stress to shear strain d. Shear rate : the rate at which the planes (or molecules) flow relative to one another Y X () = dt dr . A F FIGURE 3.3 Representation of shear (tangential stress) x y POLYMER CHEMISTRY

D. Viscous flow of molten polymer.
a. Definition of viscosity : restriction of flow. b. Function of temperature (Kinetic energy). Arrhenius-type equation: (A: constant, Ea: activation energy for viscous flow) η = Ae-Ea/RT logMW logηO Mc FIGURE 3.7. Effect of molecular weight on Newtonian viscosity. c. Function of molecular weight. d. Function of molecular structure. Intermolecular force. POLYMER CHEMISTRY

. E. Newtonian fluid a. To obey Newton's law.
a. To obey Newton's law. τ= η (η : constant, viscosity) b. Unit of viscosity : poise = dyne s/cm2 Pascal-second = newton s/m2 c. Examples of viscosity for common fluids. air : 10-5 Pas, water : 10-3 Pas, glycerin : 1 Pas, molten polymer : 102～106 Pas . POLYMER CHEMISTRY

FIGURE3.4. Types of shear flow (A) Newtonian; (B) Bingham Newtonian; (c) shear thinning
(pseudoplastic); and (D) shear thickening (dilatant). B D A C Shear stress Shear rate

F. Non-newtonian fluid a. Bingham Newtonian fluid: initiation and flow. b. Psudo plastic fluid deviated Newtonian fluid. 1) Shear thinning fluid. 2) Shear thickening fluid. log log . FIGURE3.5. Power law plots: (A) Newtonian (slope=1); (B) Shear thinning (slope<1); and (C) shear thickening (slope>1). A B C c. Shear thinning: thixotropic effect. High viscosity at low stress: entanglement. Low viscosity at high stress: disentanglement. τ= AγB (A: constant, B: index of flow) If B=1 and A= η, then Newtonian fluid. (Commercial paint is thixotropic fluid.) . Increasing shear rate POLYMER CHEMISTRY FIGURE3.6. Shear thinning arising from disentanglement.

. d. Molecular weight distribution and thixotropic effect. Narrow
Broad distribution log η . log  FIGURE 3.8. Effect of molecular weight distribution on shear thinning.

. G. Viscometer for molten polymer.  η =  2R3Ω 3M Ω kM =  Ω
Cone Polymer Plate R Ω FIGURE 3.9. Cone-plate rotational viscometer.  POLYMER CHEMISTRY

3.4 Glass Transition Temperature
A. Definition of Glass Transition Temperature. a. The temperature at which the glassy state is changed into the rubbery state. b. the glassy state: short-range vibrational and rotational motion of atoms → hard, rigid and brittle. c. the rubbery state: long-range rotational motion of segments (20-50 atoms) → soft and flexible. POLYMER CHEMISTRY

B. Change of physical properties at Tg. a. Specific volume : increase free volume above Tg. b. Enthalpy(ΔH) change : kinetic energy of segmental motion. c. Refractive index : change of density. d. Modulus : glass → rubber e. Heat conductivity : free volume. POLYMER CHEMISTRY

Mn C. Factors influencing Tg. a. Molecular weight for polystyrene =3,000 Tg=40℃, =300,000 Tg=100℃. b. Free volume : space for segmental motion. plasticizer, flexible side chain. c. Degree of freedom of internal rotation. d. Chemical structure POLYMER CHEMISTRY

Chemical Structure 1) Intermolecular forces
( Hydrogen bond, dipole-dipole interaction). to restrict segmental motion. Poly(vinyl alcohol) Tg : 85℃ (hydrogen bond) Polystyrene Tg: 100℃ Poly(4-vinylpyridine) Tg : 142℃ (dipole-dipole interaction of pyridine ring) Chemical Structure POLYMER CHEMISTRY

2) Substituent or pendent group : to restrict rotation
Polyethylene Tg : -20℃ Polypropylene Tg : 5℃ Polystyrene Tg : 100℃ Poly(2-vinylnaphthalene) Tg : 151℃ POLYMER CHEMISTRY

3) Chain stiffness of backbone.
Aliphatic polyester Tg : -63℃ PET Tg : 80℃ Polybenzimidazole Tg : 429℃ O POLYMER CHEMISTRY

4) Side chains of linear long alkyl group.
: increase side chain length, decreased Tg TABLE 3.1. Glass Transition Temperature (Tg) of Representative Vinyl Polymersa Number 4 5 6 7 8 9 10 11 12 13 14 15 Polyethylene Polypropylene Poly(1-butene) Poly(1-pentene) Poly(1-hexene) Poly(1-heptene) Poly(1-decene) Poly(1-dodecene) Poly(3-methyl-1-butene) Poly(4-methyl-1-pentene) Poly(3,3-dimethyl-1-butene) Poly(5-methyl-1-hexene) R H CH3 CH3CH2 n-C3H7 n-C4H9 n-C5H11 n-C8H17 n-C10H21 CH(CH3)2 CH2CH(CH3)2 C(CH3)3 CH2CH2CH(CH3)2 Tg(oC) -20 -24 -40 -50 -31 -41 -6 50 29 64 -14 Polymer POLYMER CHEMISTRY

Poly(4,4-dimethyl-1-pentene) Poly(vinyl n-butyl ether)
Polymer Number 16 17 18 19 20 21 22 23 Poly(4,4-dimethyl-1-pentene) Poly(vinyl n-butyl ether) Poly(vinyl t-butyl ether) Poly(vinyl chloride) Poly(vinyl alcohol) Polystyrene Poly(2-vinylnaphthalene) Poly(4-vinylpyridine) R O-C4H9-t Cl OH C6H5 CH2C(CH3)3 O-C4H9-n Tg(oC) 59 -55 88 81 85 100 151 142 TABLE 3.1. Glass Transition Temperature (Tg) of Representative Vinyl Polymersa POLYMER CHEMISTRY

5) Cis-trans isomer of diene polymer : no generalization
TABLE 3.3. Glass Transition Temperature (Tg) of Diene Polymers Tg(oC) Polymer Cis trans -58 -70 -40 1,4-Polybutadienea 1,4-Polyisopreneb 1,4-Polychloroprenea -102 -67 -20 aData from Peyser14a bData from Burfield and Lim.15 POLYMER CHEMISTRY

c. Atactic (heterotactic: no stereoregularity).
3.5 Stereochemistry A. Tacticity a. Isotactic b. Syndiotactic c. Atactic (heterotactic: no stereoregularity). FIGURE Stereoregular polymers derived from monomer CH2=CHR. Isotactic Syndiotactic

B. Erythro and threo form. a. Disubstituted vinyl monomer (RCH=CHR').
POLYMER CHEMISTRY no tacticity CH2=CR2. (3.1) (3.2) B. Erythro and threo form. a. Disubstituted vinyl monomer (RCH=CHR'). Threo-diisotactic Erythro-diisotactic Disyndiotactic FIGURE Stereoregular polymers derived from monomer RCH=CHR'.

b. Cyclobutene monomer. Erythro-diisotactic Erythro-disyndiotactic
FIGURE Stereoregular polymers derived from cyclobutene. Erythro-diisotactic Erythro-disyndiotactic Threo-diisotactic Threo-disyndiotactic

c. Disubstituted diene monomer.
RCH=CH-CH=CHR' 1) Depend on monomer form(cis or trans), initiator, temperature and solvent polarity. 2) To exist cis-trans isomers. FIGURE Two stereoregular 1,4-polymers derived from monomer RCH=CH CH=CHR’. Trans-erythro-diisotactic Cis-threo-disyndiotactic

3.5 Stereochemistry C. Hemitactic D. Stereoregularity
a. Hemiisotactic b. Hemisyndiotactic D. Stereoregularity a. To lead crystallinity. b. To influence Tg. 1) Tg of syndiotactic is higher than Tg of isotactic. 2) Tg of atactic is similar to Tg of syndiotactic. 3) It's hard to determine Tg for high crystalline polymers. POLYMER CHEMISTRY

Poly(methyl methacrylate) Poly(ethyl methacrylate)
TABLE 3.4. Glass Transition Temperature (Tg) of Polymers of Varying Tacticitya Tg(oC) Polymer Syndiotactic Atactic Isotactic Poly(methyl methacrylate) Poly(ethyl methacrylate) Poly(t-butyl methacrylate) Polypropyleneb Polystyrene 105 65 114 -4 100c 105 65 118 -6 38 12 7 -18 99c aData from Peyser14a unless otherwise noted. bData from Burfield and Doi.23 cData from lshihara, Kuramoto, and Uoi, Macromolecules, 21, 3356 (1988). POLYMER CHEMISTRY

3.6 Crystallinity A. Requirements for crystallization.
a. Regularity of molecular structure. b. Intermolecular forces. B. Inducing crystallinity. a. Cooling. b. Annealing : heating at a specified temperature, inert atmosphere. c. Stretching : orientation. POLYMER CHEMISTRY

C. Models of crystallinity
a. Fringed micelle model for low crystallinity. FIGURE Schematic representation of a polymer matrix showing crystalline regions (fringed micelle model). Crystallnity imbedded in amorphous matrix. POLYMER CHEMISTRY

b. Folded-chain lamella model for high crystallinity.
Single crystal : lamella form. Thickness of lamella : 100Å. Chain folded perpendicularly. FIGURE Folded-chain lamella model : (a) regular adjacent folds; (b) irregular adjacent folds; and (c) nonadjacent switchback.

C. Models of crystallinity
c. Extended-chain crystals. No micelle and no folded chain. Needle form, low molecular weight by slow crystallization. Molecular regularity : not necessary. d. Spherulites Aggregation of small hairlike strands. Clusters in an essentially radical pattern. Nucleation : homogeneous nucleation, heterogeneous nucleation(silica). e. Epitaxial crystallinity One crystalline growth on another. Shish Kebab type. (a) (c) (b) FIGURE Some crystalline morphologies: (a) spherulitic; (b) drawn fibrillar; and (c) epitaxial (shish kebab).

D. Properties of crystalline polymers
a. Tougher. b. Stiffer. c. Opaque : light scattering. d. Resistant to solvents. e. Higher density. POLYMER CHEMISTRY

E. Relationship between structure and crystallinity
a. crystalline structure. 50 51 52 (melting point 220oC) Crystalline 54 (melting point 140oC) O POLYMER CHEMISTRY

E. Relationship between structure and crystallinity
b. Amorphous structure. 53 Noncrystalline O POLYMER CHEMISTRY

3.7 Liquid Crystallinity A. Definition of liquid crystallinity
a. Liquids which exhibits anisotropic behavior. b. Molecules are ordered in liquid. c. The ordered regions in the liquid are called mesophases. B. Two types of liquid crystal molecules. a. Low molecular weight liquid crystals which have been studied since 1960. b. Polymeric liquid crystals which have been studied since 1970s. POLYMER CHEMISTRY

3.7 Liquid Crystallinity C. Classifications of liquid crystals.
a. Lyotropic liquid crystals : to form under the influence of solvent. b. Thermotropic liquid crystals : to form in the melt. D. Orientation of molecules in the mesophase. a. Nematic b. Smetic c. Cholesteric d. Discotic, etc. POLYMER CHEMISTRY

[From Jackson and Kuhfuss,37 copyright 1976. Reprinted by permission
FIGURE Effect of p-hydroxybenzoic acid concentration on melt viscosity of a terephthslic acid/p-gydroxybenzoic acid/ethylene glycol copolyester. [From Jackson and Kuhfuss,37 copyright Reprinted by permission of John Wiley & Sons, Inc.] Melt viscosity (275oC) poise P-Hydroxybenzoic acid, mol-% 102 105 104 103 Shear rate, s-1 15 100 1600 54,000 POLYMER CHEMISTRY

FIGURE 3.19. Representations of mesogenic groups (box) and flexible spacers ( )
in (a) the backbone and (b) the side chain of liquid crystalline polymers. (a) (b) POLYMER CHEMISTRY

E. Commercial liquid crystal polymer
a. Copolyester ( thermotropic liquid crystal ) : Trade name : Vectra ( ) 55 56 57 b. Aromatic polyamide ( lyotropic liquid crystal ): Trade name : Kevlar 58 POLYMER CHEMISTRY

F. Advantage and disadvantage of liquid crystal polymer.
a. Advantage : low viscosity. high tensile strength. b. Disadvantage : high melting transition. poor solubility. c. Circumventing these difficulties : in cooperation spacer onto rigid backbone. spacer 59 60 61 POLYMER CHEMISTRY

3.8 Chemical Crosslinking
A. Definition and physical property change. a. Linking the polymer chains together through covalent or ionic bonds to form a network. b. Not to be soluble but swelling by any solvent. c. Not to be melted but decompose at any temperature. d. For ionic crosslinking, to be melted at high temperature. POLYMER CHEMISTRY

B. The method of chemical crosslinking.
a. Simultaneously crosslinking during polymerization, using polyfunctional monomer. b. Stepwise crosslinking. First step : to make free polymer (linear or branched polymer). Second step : curing step to be made network from free polymer. POLYMER CHEMISTRY

C. Gel b. Microgel: small particles of gel(300～1000㎛)
a. Swollen crosslinked polymer. b. Microgel: small particles of gel(300～1000㎛) c. Packed microgel can be suspended in solvents. d. Microgel can be used in solid-phase synthesis (techniques for immobilizing catalysts). POLYMER CHEMISTRY

3.8 Chemical Crosslinking
D. Crosslink Density(Γ) a. The number of crosslinked monomer units per main chain. b. : the number average molecular weight of uncrosslinked polymer : the number average molecular weight between crosslinks. c. High crosslink density: hard and embrittlement. Low crosslink density: Elastomer (about one crosslink per 100monomer units). E. Telechelic Elastomer: Reactive chain ends that become incorporated into the network on crosslinking. Γ= (Mn)c (Mn)o (Mn)c (Mn)o POLYMER CHEMISTRY

3.9 Physical Crosslinking.
A. Definition a. Not covalent crosslink but strong secondary force attraction between polymer chains. b. Physical crosslinked polymer can be recycled. B. Examples of physical crosslinking. a. Crystalline polymer : To act like crosslinked amorphous polymer. b. Hydrogen bond : Gelatin, an animal-derived protein. c. Block copolymer : A-B-A type. A : styrene, short-hard segment, microdomain. B : butadiene, long-soft segment, matrix. d. TPE : Thermoplastic elastomer. POLYMER CHEMISTRY

FIGURE 3.20 Representation of aggregation in an ABA block thermoplastic elastomer
( represents end blocks, circle represents microdomains).

TABLE 3.6. Commercially Important Thermoplastic Elastomers
Type End Blocks Middle Block Polystyrene Isotactic polypropylene Rigid polyurethane Rigid polyesterb Rigid polyamidec Polybutadiene or polyisoprene Ethylene-propylene copolymer Flexible polyester or polyether Flexible polyester Flexible polyether Styrenic Polyolefina Polyurethane Copolyester Polyamide a Also manufactured by mechanical blinding of isotactic polypropylene and ethylene-propylene-diene copolymer. b Principally poly(ethylene terephthalate). c Nylons 6, 66, 11, 12, and 612. POLYMER CHEMISTRY

3.10 Polymer Blends A. Definition of polymer blends.
a. Physical mixture of two or more different polymer or copolymer. b. No covalent bonds among the polymers. c. Polymer alloys : like metal alloys. d. Blending is much easier than developing new polymers. B. Technology of polymer blendings. POLYMER CHEMISTRY

TABLE 3.7. Types of Polyblends
Mechanical blends Mechanochemical blends Solution-cast blends Latex blends Chemical blends Interpenetrating polymer networks (IPN) Semi-interpenetrating polymer networks (semi-IPN) Semultaneous interpenetrating polymer networks (SIN) Interpenetrating elastomeric networks (IEN) Description Polymers are mixed at temperatures above Tg or Tm for amorphous and semicrystalline polymers, resectively Polymers are mixed at shear rates high enough to cause degradation. Resultant free radicals combine to form complex mixtures including block and graft components Polymers are dissolved in common solvent and solvent is removed Fine dispersions of polymers in water (latexes) are mixed, and the mixed polymers are coagulated Crosslinked polymer is swollen with different monomer, then monomer is polymerized and crosslinked Polyfunctional monomer is mixed with thermoplastic polymer, then monomer is polymerized to network polymer (also called pseudo-IPN) Different monomers are mixed, them homopolymerized and crosslinked simultaneously, but by noninteracting mechacisms Latex polyblend is crosslinked after coagulation

C. Miscible polymer blends.
a. Homogeneous one phase blends like solution. b. To show single Tg. c. Semiempirical relationship of properties for homogeneous binary system. P = P1Φ1 + P2Φ2 + IΦ1Φ2 P : Properties of blends. Φ : The volume fraction. P1,P2 : Properties of polymer components 1,2 I : Interaction term. ( I = 0 : strictly additive, I > 0 : synergistic, I < 0 : nonsynergistic. ) d. Glass transition temperature of miscible blends. Tg = w1Tg1 + w2Tg ( w : weight fraction, Tg : kelvins ) POLYMER CHEMISTRY

C. Miscible polymer blends.
e. Commercial examples of miscible blends. 1) Noryl (GE) : polystyrene + PPO. poly(oxy-2,6-dimethyl-1,4-phenylene) Tensile strength : synergic. 2) LDPE + EPDM(ethylene-propylene-diene monomer rubber). Tensile strength : synergic. f. Stereochemistry is important for miscibility. syndiotactic poly(methylmethacrylate) + poly(vinyl chloride) : miscible. isotactic poly(methylmethacrylate) + poly(vinyl chloride) : immiscible. POLYMER CHEMISTRY

D. Immiscible polymer blends.
a. Because of immiscibility, to appear phase separation and to show poor mechanical property. b. Methods of mixing effectively for immiscible blends. 1) IPN techniques. 2) Using compatibilizer like A-B block copolymer or graft copolymer. FIGURE Representation of the use of an AB block copolymer to improve interfacial adhesion in an immiscible polyblend. Poly (A) Poly (B) A B 3) Example of this methodology. : ABS (acrylonitrile-butadiene-styrene) plastics. amorphous styrene-butadiene copolymer + graft copolymer styrene monomer (chain-transfer) + copolymerization acrylonitrile monomer ABS

Chapter 4. Chemical Structure and Polymer Properties
4.1 Introduction 4.2 Fabrication Methods. 4.3 Mechanical Properties 4.4 Thermal stability 4.5 Flammability and Flame Resistance. 4.6 Chemical Resistance. 4.7 Degradability 4.8 Electrical Conductivity 4.9 Nonlinear Optical Properties POLYMER CHEMISTRY

4.1 Introduction A. Relationship between chemical structure and polymer properties. a. Chemical structure and morphology (Chapter 3). b. Polymer properties : mechanical property, thermal property, chemical property, electrical property, etc. B. To tailor chemical structure for specialty polymer. C. Additives - compounds to modify polymer property. D. Fabrication method to make polymer articles. POLYMER CHEMISTRY

4.2 Fabrication Methods. A. Molding
a. Compression molding : thermoset polymer. FIGURE 4.1. Compression molding POLYMER CHEMISTRY

b. Injection molding : thermoplastic polymer.
FIGURE 4.2. Injection molding. [Reprinted from V. Hopp and I. Hennig, Handbook of Industrial Chemistry, copyright 1938, courtesy of McGraw-Hill.] POLYMER CHEMISTRY

c. Reaction injection molding (RIM)
FIGURE 4.3. Basic components of a reaction injection molding (RIM) process. [From Modern Plastics Encyclopedia, Reprinted with permission of Modern Plastics.] newly developed molding. polyurethane and other polymer system. POLYMER CHEMISTRY

d. Reinforced reaction injection mold (RRIM) :
A. Molding d. Reinforced reaction injection mold (RRIM) : Modified RIM for fiber reinforcement. e. Blow molding : for bottles. FIGURE 4.4. Blow molding. [Courtesy of the Society of the Plastics, Inc.] POLYMER CHEMISTRY

4.2 Fabrication Methods. B. Casting : for making film.
a. Solution casting and melting casting. b. Calendering : thick film. C. Extrusion : to make rods and pipe. a. Extruder : screw of injection mold + die instead of mold. b. sometimes to make thin film by extrusion. ex) PE film. POLYMER CHEMISTRY

a. melt spinning : for molten polymer. b. dry spinning
D. Spinning. v a. melt spinning : for molten polymer. b. dry spinning c. wet spinning : solvent soluble polymer. Fig.4.5 Basic components for spinning.

E. Blowing agent : for foamed plastic.
a. Physical blowing agent. 1) Gas : air, nitrogen, carbon dioxide. 2) Low-boiling liquid : pentane, CFC (not to be used now, because of ozone depletion) b. Chemical blowing agent. 1) Byproduct CO2 for polyurethane synthesis. 2) Decompose on heating and give off nitrogen. POLYMER CHEMISTRY

4.3 Mechanical Properties
A. Molecular weight dependent mechanical properties. a. For vinyl polymer, molecular weight : 105 For polyamide, molecular weight : 20,000 ～ 50,000 b. For small molecular weight, properties of end group : significant In case of high molecular weight : negligible. c. Properties and molecular weight. POLYMER CHEMISTRY

Property Molecular weight Mechanical Working range Nonmechanical FIGURE 4.6. Dependence of properties on molecular weight (hypothetical polymer). Viscosity

B. Type of mechanical properties. a. Tensile strength, tensile modulus, elongation. b. Compressive strength : reverse tensile strength. c. Flexural strength : Impact resistance, abrasion resistance, tear resistance, hardness POLYMER CHEMISTRY

C. Tensile strength. a. Important and useful mechanical property. 1) Tensile stress : 2) Tensile strain : 3) Tensile modulus : b. Units of tensile strength : 1) CGS : dyne / cm2 2) SI : N / m2 (Pa) 3) pounds per square inch (psi)  = A F  = l l E =   c. Unit of modulus same unit of tensile strength. d. Unit of elongation : No dimension. POLYMER CHEMISTRY

Fiber Brittle plastic Stress () Elastomer Strain () FIGURE 4.7. Characteristics of tensile stress-strain behavior.

FIGURE4.8. General tensile stress-strain curve for a typical thermoplastic.
Elongation at break Elongation at yield Stress () Yield stress Strain () Ultimate strength

D. Temperature dependent mechanical properties
a. The modulus of amorphous thermoplastic depend on temperature. FIGURE 4.9. Effect of temperature on tensile modulus of an amorphous thermoplastic; log E, modulus scale; Tg, glass transition temperature. Glassy Rubbery Flow Temperature log E (N/m2) Tg 3 6 9

b. Tensile modulus of crystalline and crosslink polymer depend on temperature.
FIGURE Effect of temperature on tensile modulus (log E scale) of various polymers. Tm, crystalline melting temperature. [Reprinted with permission from J. J. Aklonis, J. Chem. Educ., 58, 11 (1981).] Temperature log E (N/m2) Crystalline Highly crosslinked Lightly Low molecular weight High weght 3 6 9 Tm

> 4.3 Mechnical Properties E. Time dependent mechanical properties
a. viscoelastic property b. creep stress relaxation > disentanglement by stress like as temperature F. General relationship between mechanical property and structure. a. Flexible backbone : lower tensile property b. Chain stiffness of backbone or bulky side group : increase tensile property c. Chain stiffness : lower impact strength. cf) Table 4.1 and Table 4.2 d. Tensile strength of fiber Tenacity= N/ tex , tex= gram / 1000meters of the fiber. POLYMER CHEMISTRY

aValues taken from Aranoff,12a converted to SI units, and rounded off.
TABLE 4.1. Mechanical Properties of Common Homopolymersa Polymer Polyethylene, low density high density Polypropylene Poly(vinyl chloride) Polystyrene Poly(methyl methacrylate) Polytetra- fluoroethylene Nylon 66 Poly(ethylene terephthalate) Polycarbonate Strengthb (Mpa) 8.3-31 22-31 31-41 41-52 36-52 48-76 14-34 76-83 48-72 66 Modulusb - 2380 Elongation (%) 40-80 2-10 60-300 50-300 110 Compressive 20-25 38-55 55-90 83-90 72-124 12 103 76-103 86 Flexural 41-55 69-110 69-101 72-131 42-117 96-124 93 Impact Strengthc (N/cm) No break 1.7 9.1 Tensile Properties at Break Property aValues taken from Aranoff,12a converted to SI units, and rounded off. bTo convert megapascals to pounds per square inch, multiply by 145. cIzod notched impact test (see Chap. 5). To convert newtons per centimeter to foot pounds per inch, multiply by 1.75.

TABLE 4.2. Fiber Propertiesa
Fiber Type Natural Cotton Wool Synthetic Polyester Nylon Aromatic polyamide (aramid)c Polybenzimidazole Polypropylene Polyethylene (high strength) Inorganicc Glass Steel Tenacityb (N/tex) 0.27 2.65d 0.31 Specific Gravity 1.50 1.30 1.38 1.14 1.44 1.43 0.90 0.95 2.56 7.7 aUnless otherwise noted, data taken form L. Rebenfeld, in Encyclopedia of Polymer Science and Engineering (H. f. Mark, N. M. Bikales, C. G. Overberger, G. Menges, and J. I. Kroschwitz, Eds.), Vol. 6, Wiley-Interscience, New York, 1986, pp bTo convert newtons per tex to grams per denier, multiply by 11.3. cKevlar (see Chap. 3, structure 58.) dFrom Chem. Eng. New, 63(8), 7 (1985). eFrom V. L. Erlich, in Encyclopedia of Polymer Science and Technology (H.F. Mark, N. G. Gaylord, and N. M. Bikales, Eds.), Vol. 9, Wiley-Interscience, New Uork, 1968, p. 422.

4.4 Thermal stability A. Chemical structure of thermally stable polymer: to have aromatic repeating unit. TABLE 4.3. Representative Thermally Stable Polymersa Decomposition Temperature (oC)b 660 650 640 620 Type Poly(p-phenylene) Polybenzimidazole Polyquinoxaline Polyoxazole Structure

TABLE 4.3. Representative Thermally Stable Polymersa
Decomposition Temperature (oC)b 585c 570 490 Type Polyimide Poly(phenylene oxide) Polythiadiazole Poly(phenylene sulfide) Structure aData from Korshak17 bNitrogen atmosphere unless otherwise indicated. cHelium atmosphere. POLYMER CHEMISTRY

B. Aromatic or cyclic repeating unit
a. Thermal stability : to bonds cleavage for degradation b. Poor processability 1) High Tg or high Tm 2) High viscosity of molten polymer 3) Low solubility c. Incorporation of inorganic material. d. Seurcumvent of poor processability 1) Incorporation of flexible chain on backbone or side chain. 2) Insertion of heteroatom. 3) Symmetry→ asymmetry POLYMER CHEMISTRY

C. Carl S. Marvel: polybenzimidazole fiber
a. Astronaut's space suits and firefighters' protective clothing. b. Cardo polymer (from the Latin cardo, loop) c. Cyclic aromatic groups that lie perpendicular to the planar aromatic backbone. d. Improved solubility with no sacrifice of thermal properties. 1 2 POLYMER CHEMISTRY

D. Cycloaddition to make cyclic repeating unit.
Tg = 215oC Tg = 265oC SCHEME 4.1. Increasing Tg of a polyquinoxaline by intramolecular cycloaddition.

E. Oligomers with reactive End Group.
TABLE 4.4. Some Reactive End Groups for Converting Oligomers to Network Polymers Type Sturcture Cyanate Ethynyl Maleimide Nadimidea Phenylethynyl aCommon name for 5-norbornene-2,3-dicarboximide.

4.5 Flammability and Flame Resistance.
A. Process of flame propagation. Solid polymer -(heat)→ Depolymerization to monomer(radical formation) → Degradation to combustable gas → Flame formation. FIGURE Representation of polymer combustion , gas diffusion; , heat flux. [Adapted from Factor.43] Diffusion zone Flame front Pyrolysis Solid polymer

B. The object of flame retardation. a. Suppression of smoke and toxic gases. b. Development of nonflammable polymer: self-extinguishing. C. The strategies of flame resistance. a. Retarding the combustion process in the vapor phase. b. Causing "char" formation in the pyrolysis zone. c. Giving nonflammable gas or cooling the pyrolysis zone. POLYMER CHEMISTRY

D. Examples of flame resistance. a. Halogen containing polymer: to suppress radical concentration. b. Addition antimony oxide to be formed antimony halide. c. Phosphorus-containing polymers: promotion char. d. Aromatic and network polymers: to promote char. e. Addition Al2O3 · 3H2O to evolve water. POLYMER CHEMISTRY

4.6 Chemical Resistance. A. Types of chemical reaction.
a. Free radical reaction by oxygen or UV-light. b. Hydrolysis. c. Ozonolysis. POLYMER CHEMISTRY

4.6 Chemical Resistance. B. Preventing hydrolysis.
a. Chemically resistant polyester formulations. 7 8 POLYMER CHEMISTRY

4.6 Chemical Resistance. B. Preventing hydrolysis.
b. End group blocking. POLYMER CHEMISTRY

C. Moisture resistance and chemical inertness: fluorinated polymer.
a. Fluorinated phosphazene. 9 10 b. Teflon and copolymer. 11 12 13 POLYMER CHEMISTRY

a. Ozonolysis mechanism.
D. Ozonolysis a. Ozonolysis mechanism. b. Preventing ozonolysis: to add cyclopentadiene. 14 POLYMER CHEMISTRY

4.6 Chemical Resistance. E. Sunlight protection.
Monomers containing ultraviolet-absorbing chromophore. 15 F. Morphology a. Crystallinity to prevent penetration. b. Crosslinking POLYMER CHEMISTRY

4.7 Degradability A. Application for polymer degradability.
a. Polymer waste treatment. 1) Photodegradable polymer containing carbonyl functional group. Norrish type II degradation reaction. 2) Biodegradable polymer by microbiology. Poly(α-hydroxybutanoic acid), starch+PE POLYMER CHEMISTRY

A. Application for polymer degradability.
b. Photoresist for IC. 1) Positive resists: radiation promotes degradation of the resist exposed by the mask. 2) Negative resists: radiation makes insoluble network. FIGURE Schematic of a typical procedure for producing (a) negative resists and (b) positive resists in the manufacture of integrated circuits.

A. Application for polymer degradability.
c. Agricultural degradable mulches. 1) Starch-graft-poly(methylacrylate). 2) Block copolymers of amylose or cellulose with polyester. d. Surgical sutures and implanted polymeric matrix devices. POLYMER CHEMISTRY

B. Controlled release: penetration rather than degradation.
a. Microencapsulation. b. Strip. FIGURE Membrane-controlled release devices: (a) microencapsulation, and (b) strip. POLYMER CHEMISTRY

c. 2,4-Dichlorophenoxyacetic acid(2,4-D): herbicide. Vinyl polymer with hydroyzable pendant group, chelate with iron. d. Pheromone release strips: insecticides. e. Transdermal patches. 1) Nitroglycerin to treat angina. 2) Scopolamine to treat combat motion sickness. POLYMER CHEMISTRY

f. Phosphazene polymer. R= amino acids, esters, steroids g. Poly(N-isopropylacrylamide) 1) 2) To shrink reversibly in response to temperature increase. 3) Incorporation with IPN. POLYMER CHEMISTRY

4.8 Electrical Conductivity
A. Classification of electrical conductivity. a. Insulator : σ < 10-8 S/ cm b. Semiconductor: 10-7 < σ < 10-1 S/ cm c. Conductor: σ > 102 S/ cm (σ=conductivity, S (simen)= 1/Ω) POLYMER CHEMISTRY

B. Theory of electrical conductivity for polyacetylene.
a. Soliton. 1) Delocalization regions of conjugated double bond. 2) Extend about 15 bond lengths. 3) Energy gain arising for stabilization. 4) Electron transfer via positive or negative solitons FIGURE4.14. Proposed conducting unit of polyacetylene. Soliton may be neutral (radical), positive (carbocation), or negative (carbanion). Soliton

B. Theory of electrical conductivity for polyacetylene.
b. Doping: incorporation dopant much as AsF5, I2, Lewis acid, etc. + dopant : 1.5×105 S/cm 22 23 2 CH CH [ ] + 3 I2 + + 2 I3- - + Na + Na+ POLYMER CHEMISTRY

C. Example of conducting polymers.
a. Poly(N-vinyl-carbazole) 1) Photoconducting: conduct small degree of electricity under the light. 2) Electrophotography(photocopying) 19 b. Poly(sulfur nitride): Super conductor 20 POLYMER CHEMISTRY

c. Polyaniline Polypyrrole Polythiophene
c. Polyaniline Polypyrrole Polythiophene Poly(p-phenylene) Poly(p-phenylenevinylene) d. Conducting polymers to be used as light emitting diode. (PPV) C. Example of conducting polymers. 24 25 26 28 27 e. Conducting polymers much lower density than metal. polymer=1g/cm3, copper=8.92g/cm3, Gold=19.3g/cm3 POLYMER CHEMISTRY

Poly(p-phenylenevinylene) Polyaniline Polypyrrole Polythiophene
TABLE 4.5. Conductivities of Metals and Doped Polymersa Material Copper Gold Polyacetylene Poly(sulfur nitride) Poly(p-phenylene) Poly(p-phenylenevinylene) Polyaniline Polypyrrole Polythiophene 5.8  105 4.1  105 103 – 105 103 – 104 103 102 – 103 102 Conductivity (S/cm)b aData from J. R. Reynolds, A. D. Child, and M. B. Gieselman, in Encyclopedia of Chemical Technology, 4th ed. (J. I. Kroschwitz and M. Howe-Grant, Eds.), Wiley, New York, 1994; and Chem. Eng. News, Jume 22, 1987, p. 20. bI siemen (S) = I ohm-1. POLYMER CHEMISTRY

4.8 Electrical Conductivity
D. Polyelectrolytes for solid battery. 30 29 POLYMER CHEMISTRY

4.9 Nonlinear Optical Properties
A. Photonics device. a. Information and image processing. b. To operate higher rate. c. To store information much more densely. POLYMER CHEMISTRY

B. NLO materials a. Inorganic and low molecular weight organic compounds. b. Polymeric materials 1) Conjugated double bond like conducting polymer: Third order harmonic generation. 2) Asymmetric strong dipole aromatic molecule: Second order harmonic generation 3) Containing strong electrowithdrawing and donating group: Second order chromophore. 4) Dipole molecules must be poled at Tg. 5) Stabilizing poled molecule to avoid relaxation. POLYMER CHEMISTRY

C. Producing NLO polymeric material. a. Host-Guest combination. Host: matrix polymer. Guest: NLO chromophore. b. Incorporating chromophore in the polymer backbone or side chain covalently. POLYMER CHEMISTRY

4.10 Additives A. Purpose of using additives.
a. To alter the properties of the polymer. b. to enhance processability. B. Types of polymer additives. C. Examples of polymer additives. a. Plasticizer. 1) Internal plasticizer, to have covalent bonds between polymer and plasticizer. 2) External plasticizer, physical mixture with plasticizer. POLYMER CHEMISTRY

TABLE 4.6. Polymer Additives
Type Mechanical property modifiers Plasticizers Impact modifiers Reinforcing fillers Nucleating agents Surface property modifiers Slip and antiblocking agents Lubricants Antistatic agents Coupling agents Wetting agents Antifogging agents Chemical property modifiers Flame retardants Ultraviolet stabilizers Antioxidants Biocides Aesthetic property modifiers Dyes and pigments Odorants Deodorants Processing modifiers Slip agents and lubricants Low-profile additives Thickening agents Heat stabilizers Defoaming agents Blowing agents Emulsifiers Crosslinking (curing) agents Promoters Increase flexibility Improve impact strength Increase strength properties Modify crystalline morphology Prevent film and sheet sticking Prevent sticking to machinery Prevent static charge on surfaces Improve bonding between polymer and filler Stabilize dispersions of filler Disperse moisture droplets on films Reduce flammability Improve light stability Prevent oxidative degradation Prevent mildew Impart color Add fragrance Prevent development of odor Improve light transmission Reduce melt viscosity Prevent sticking to processing machinery Prevent shrinkage and warpage Increase viscosity of polymer solutions or dispersions Prevent degradation during processing Reduce foaming Manufacture stable foams Stabilize polymer emulsions Crosslink polymer Speed up crosslinking (curing) Function

b. TABLE 4.7. Commonly Used Plasticizers Aromatic
Di-2-ethylhexyl phthalate Di-n-octyl phthalate Di-i-octyl phthalate Di-i-decyl phthalate Di-n-undecyl phthalate Di-n-tridecyl phthalate Tri-2-ethylhexyl trimellitate Aliphatic Di-2-ethylhexyl adipate Di-2-ethylhexyl sebacate Di-2-ethylhexyl azelate Epoxy Epoxidized linseed oil Epoxidized soya oil Polymeric Poly(alkylene adipates, sebacates, or azelates) Fire retardant Chlorinated paraffins Phosphate esters b. POLYMER CHEMISTRY

C. Producing NLO polymeric material.
c. Reinforcing material: Composite. 1) Carbon black for tire. 2) Glass fiber for FRP. 3) Aromatic polyamide or graphite fiber for high performance engineering plastic. POLYMER CHEMISTRY

Chapter 5. Evaluation, Characterization, and Analysis of Polymers
5.1 Introduction. 5.2 Chemical Methods of Analysis. 5.3 Spectroscopic Methods of Analysis. 5.4 X-ray, Electro, and Neutron Scattering 5.5 Characterization and Analysis of Polymer Surfaces. 5.6 Thermal Analysis 5.7 Measurement of Mechanical Properties. 5.8 Evaluation of Chemical Resistance. 5.9 Evaluation of Electrical Properties. POLYMER CHEMISTRY

5.1 Introduction. A. Complexities of polymer characterization.
a. The complexity of molecules: configuration and information. b. The complexity of polymer morphology: crystalline and amorphous state. c. Variability of additives: mixture type of materials. POLYMER CHEMISTRY

5.1 Introduction. B. Types of polymer characterization.
a. Spectroscopical analysis. b. Thermal analysis. c. Surface analysis. d. Mechanical and electrical testing. e. Chromatographic analysis. f. Chemical analysis. early traditional method by chemical reaction. Instrumental method. POLYMER CHEMISTRY

5.1 Introduction. C. Standardization for analytical methods.
a. American Society for Testing and Materials (ASTM). b. British Standards Institute (BSI). POLYMER CHEMISTRY

5.2 Chemical Methods of Analysis.
A. Periodic acid and lead tetraacetate oxidation a. To determine backbone structure of poly(vinyl alcohol). Head-to-tail or head-to-head b. To determine solution viscosity after oxidation of poly(vinyl alcohol). Decreasing solution viscosity: head-to-head structure. POLYMER CHEMISTRY

5.2 Chemical Methods of Analysis.
B. Ozonolysis for diene polymer a. To determine the backbone structure of the natural rubber. b. Degradative product: 4-Ketopentanal. c. 1-4-cis addition of isoprene. POLYMER CHEMISTRY

5.3 Spectroscopic Methods of Analysis.
TABLE 5.1. Spectroscopic and Scattering Methods Commonly Used for Studying Polymers Vibrational Infrared (IR) Raman Spin resonance Nuclear magnetic resonance (NMR) (Proton and carbon-13) Electron spin resonance (ESR) Electronic Ultraviolet (UV)-visible Fluorescence Scattering X-ray Electron Neutron

Micrometers Transmittance (%) Wave number (cm-1) FIGURE 5.1. Infrared spectrum (KBr pellets) of polyimide ( ) and model compound (----). [Reprinted from Troy, Sobanski, and Stevens,19 by courtesy of Marcel Dekker, Inc.]

5.3.1 Infrared. A. FTIR spectroscopy. a. FT: Fourier transform. Principle of Interferometry. b. Vibrational transition of chemical bonds. c. qualitative identification of unknown polymer by using DB. POLYMER CHEMISTRY

B. Analysis of Morphology. a. Annealed isotactic polystyrene: semicrystalline. b. Heating up to Tm and quenching: amorphous. c. Subtracting amorphous from spectrum crystalline spectrum. Figure 5.2. Fourier transform-in-frared spectra of isotactic polystyrene in the 640 to 840 cm-1 region: (A) semicrystalline; (B) amorphous; and (c) the difference spectrum obtained by subtracting B from A. [From Painter and Koening,21 copyright Reprinted by permission of John Wiley & Sons, Inc.]

C. Characterization of blends: Noryls(PS+PPO). a. Immiscible blends: superposition of two spectra of homopolymers b. Miscible blends: superposition of three spectra of homopolymers and interaction spectrum. c. Interaction spectrum: dipole-dipole coupling of the benzene rings of PS+PPO. POLYMER CHEMISTRY

5.3.2 Raman A. Raman spectroscopy. a. Impinging visible light onto molecular vibrations. b. To major scattered light depended on the vibration. c. Symmetric vibration: Raman active (μ=0) d. Asymmetric vibration: IR active (μ≠0) e. Raman light: laser. complementary POLYMER CHEMISTRY

B. Applications to polymer study. a. Conformational study of polymer. b. Cis-trans isomers of elastomer. c. Sulfur crosslinked polymer. d. Water solution of polymer. POLYMER CHEMISTRY

Nuclear Magnetic Resonance. A. Nuclear Resonance. a. Detectable nuclei: odd spin quantum number H, 13C, 19F, 31P. b. Resonance energy: radiofrequency. c. Detectable parameter: chemical shift, coupling constant, integration, relaxation time. POLYMER CHEMISTRY

1) Chemical structure identification by using
B. Types of NMR. a. Solution state NMR. 1) Chemical structure identification by using 1H and 13C environment. 2) Tacticity of polymer.

FIGURE 5.3. 500-MHz 1H nuclear magnetic resonance
spectrum of isotactic poly(methyl methacrylate) (10% weight/volume solution in chlorobenwene-d5 at 100oC) at three values of gain. E, t: erythro and threo placement of methylene protons with respect to ester groups; m, r: meso and racemic dyads. [Courtesy of Dr. Frank Bovey, Bell Laboratories. From Schilling, Bovey, Bruch, and Kozlowski, 35 copyright Reprinted by permission of the American Chemical Society.]

B. Types of NMR. b. Solid state NMR. 1) Dipolar interactions and long relaxation times. 2) Anisotropy of the chemical shift in all possible directions. 3) Cross-polarization: effectively speeds up carbon's spin. 4) Magic angle spinning: at 54.7°, rapid spinning. 5) Directly majoring solid sample: Crosslinked and bulk polymers FIGURE 5.5. Solid-state proton-decoupled 13C nuclear magnetic resonance spectrum of polycarbonate (A) with and (B) without cross-polarization magic angle spinning. Peak assignments: (a) carbonyl carbon; (b) substituted Ring carbons; and (c) unsubstituted ring carbons. [From Schaefer, Stejskal, and Buchdahl,38 copyright 1977. Reprinted by permission lf the American Chemical Society.]

c. MRI: Magnetic resonance imaging.
B. Types of NMR. c. MRI: Magnetic resonance imaging. 1) A technique analogous to medical diagnosis. 2) Quality control for fabricated polymer samples. 3) Characterization of phase boundaries. 4) Monitoring penetration of fluids into polymer. POLYMER CHEMISTRY

5.3.4 Electron Spin Resonance(ESR),
Electron paramagnetic resonance(EPR). A. Principles of ESR. a. The same principles as NMR. b. Resonance energy : microwave frequencies. c. Spin transition of unpaired electon : Radical. d. ESR spectra: direct absorption curve. POLYMER CHEMISTRY

B. Applications to polymers.
a. Radical reaction(polymerization, degradation and oxidation) 1) Hyperfine splitting: six-line= 4α+1β. 2) Radical surrounded by five protons. FIGURE 5.6. Electron spin resonance spectrum of UV-irradiated poly(vinyl chloride) at -196oC. [From Yang, Liutkas, and Haubenstock,40 copyright Reprinted by permission of the American Chemical Society.]

B. Applications to polymers.
b. Spin label. Transition metal or a nitroxide radical containing polymer. c. Spin probe. To mix a compound containing an unpaired electron. Molecular motion and relaxation phenomena. POLYMER CHEMISTRY

5.3.5 Ultraviolet(UV) - visible
A. Priciples of UV-visible. a. Electronic excitation: n→π* , π→π* b. Detectable chromophore : conjugated double bond or aromatic compound. POLYMER CHEMISTRY

B. Application to polymers. a. Residual monomer, inhibitor, antioxidants contained chromophore. ex) styrene monomer. b. Evaluating copolymer composition in case of chromophore containing monomers. c. Identifying end groups. d. molar absorptivity (Beer-Lambert law). 1) Tacticity. 2) Sequence length. ) Interaction between chromophores and functional group. 4) Solvent. POLYMER CHEMISTRY

C. ORD (Optical rotatory dispersion). a. Optical rotation as a function of wavelength. b. Biopolymers, Optical active polymer. POLYMER CHEMISTRY

5.3.6 Fluorescence A. Principles of luminescence. a.
B. Fluorescent spectra. a. Intensity of the emitted light as a function of wavelength. b. Exiplexes: donor+acceptor (charge transfer complex). c. Compatibility: donor containing polymer+acceptor containing polymer. Energy transfer: miscible FIGURE Energy level diagram and summary of photochemical processes.

5.4 X-ray, Electro, and Neutron Scattering
A. X-ray scattering. a. X-ray source: b. Two types of X-ray scattering. 1) WAXS (coherently): no change wavelength or phase. 2) SAXS (incoherently): change in both wavelength and phase. c. Information from the X-ray scattering. 1) Degree of crystallinity. 2) Dimension of crystalline domains. 3) Bond distances and angles. 4) Type of conformation in the crystalline regions. POLYMER CHEMISTRY

FICURE 5. 7. Wide-angle and small-angle x-ray diffraction techniques
FICURE 5.7. Wide-angle and small-angle x-ray diffraction techniques. [From E. A. Collins, J. Bares, and F. Billmeyer, Exteriments in Polymer Science. Wiley-Interscience, copyright Reprinted by permission of Jogn Wiley & Sons, Inc.]

B. Electron scattering. a. Electron source : Cathode-ray tube. b. Transmission electron microscope (TEM) Resolution : 2 ~ 5Å (×200,000 to 500,000) c. Informations from the electron scattering. 1) Crystal dimensions. 2) Degree of crystallinity. POLYMER CHEMISTRY

B. Electron scattering. d. Advantage. 1) Both diffraction and transmission measurements. 2) Small sample size. 3) High diffraction intensity and reflection number. e. Disadvantage. 1) Causing free radical reaction. 2) Scission of crosslinking. POLYMER CHEMISTRY

C. Neutron scattering. a. Neutron source : nuclear reactor. b. Neutron detector : neutron counter. c. Information from the Neutron scattering. 1) Elastic scattering : the same information as X-ray or TEM. 2) Inelastic scattering ① Hydrogen atom movement. ② Chain folding in lamellae (short-chain). ③ Two states (solid, liquid or solution). POLYMER CHEMISTRY

5.5 Characterization and Analysis of Polymer Surfaces.
A. Area of surface analysis. a. In low molecular weight compound. 1) Catalysts. 2) Semiconductors. 3) Other electronics devices. b. In polymer. 1) Coatings 2) Interface of polymer-catalyst, polymer-filler interfaces. 3) Surface oxidation. 4) Surface morphology. POLYMER CHEMISTRY

5.5 Characterization and Analysis of Polymer Surfaces.
B. Theory of surface analysis. C. Types of surface analysis. Beam source Detection Surface of specimen D. Detection pressure : Torr POLYMER CHEMISTRY

5.5.1 Scanning Electron Microscopy (SEM)
A. Electron beam. a. Source : Cathode-ray tube. b. Fine electron incident beam. c. To be scanned across the sample surface. d. Resolution : 100Å. B. Information from SEM. a. Topology of surface or surface morphology. b. Pigment dispersions in paints. c. Blistering or cracking of coatings. d. Phase boundaries. e. Cell structure of polymer foams. f. Adhesive failures. POLYMER CHEMISTRY

5.5.2 Attenuated Total Reflectance Spectroscopy (ATR)
A. Characteristics of ATR. a. Light source : IR beam. b. To be attachable with IR. c. lower cost. d. To be attached to crystal (ThBr, AgCl). POLYMER CHEMISTRY

B. Principle of ATR. a. Angle of incident beam : greater than critical angle for reflection. b. FIGURE 5.8. Attenuated total reflectance (ATR) : (a) single reflection, and (b) multiple internal reflection (MIR)

C. Application a. Surface coating. b. Surface oxidation. c. Adhesive substrate interfaces. d. Other aspects of polymer surfaces. POLYMER CHEMISTRY

5.5.3 Photoacoustic Spectroscopy (PAS)
a. Light source : IR, UV-visible. b. Signal is very low. c. Scanning : several thousand times. B. Usefulness of PAS a. Air-or moisture sensitive polymer. b. To detect subsurface by change of modulation. POLYMER CHEMISTRY FIGURE 5.9. Schematic of the photoacoustic process.

5.5.4 Electron Spectroscopy for Chemical Analysis
(or Applications) (ESCA) and Auger Electron Spectroscopy (AES) A. ESCA EB = hv - Ekin EB : Binding energy hv : Incident X-ray Ekin : The kinetic energy of the emitted electron POLYMER CHEMISTRY

FIGURE 5.10. Schematic diagram of an electron spectroscopy for chemical analysis (ESCA) spec-
trometer. [From Rabek,67 copyright Reprinted by permission of John Wiley & Sons, Ltd.] POLYMER CHEMISTRY

Right 1979. Reprinted by permission of the American Chemical Society.]
FIGURE Electron spectroscopy for chemical analysis (ESCA) spectra of films: (A) Polystyrene and poly(ethylene oxide); and (B), (c) Polystyrne-block-poly(ethylene oxide) cast from chloroform and ethylbenzene, respectively.[From Thomas and O’Malley,69 copy- Right Reprinted by permission of the American Chemical Society.] POLYMER CHEMISTRY

5.5.4 Electron Spectroscopy for Chemical Analysis
(or Applications) (ESCA) and Auger Electron Spectroscopy (AES) B. AES a. Auger electron : 2s, 2p electrons → 1s and 2s. EB = Ekin(1s) + EB(2s) + EB(2p) b. Application : Polymer-metal interface characterization. c. Complements of ESCA. POLYMER CHEMISTRY

5.5.5 Secondary-Ion Mass Spectrometry (SIMS)
and Ion-Scattering Spectroscopy (ISS) A. Principle a. Inert gas ion (Primary ion) irradiation. b. Surface sputtering : ejection of atomic and molecular fragmentation. B. The method of Ion-scattering. FIGURE Representation of surface sputtering and primary ion elastic scattering as the basis of Secondary-ion mass spectrometry (SIMS) and ion-scattering spectroscopy (ISS), respectively.

5.5.5 Secondary-Ion Mass Spectrometry (SIMS)
and Ion-Scattering Spectroscopy (ISS) C. Example of spectra. FIGURE Secondary-ion mass spectrometry-positive ion spectrum of polytetrafluoroethylene showing surface contamination. (20Ne used as the sputtering gas.) [From Herc- ules and Hercules,71reprinted with Permission.] POLYMER CHEMISTRY

5.5.6 Atomic Force Microscopy (AFM)
A. Schematic diagram of an AFM FIGURE Schematic diagram of an atomic force microscope.

5.6 Thermal Analysis 5.6.1 Differential Scanning Calorimetry (DSC)
and Differential Thermal Analysis (DTA) A. Schematic diagram FIGURE Schematic representations of differential thermal analysis (DTA) and differential scanning calorimetry (DSC) measuring cells. [From Rabek,76 copyright 1980. Reprinted by permission of John Wiley & Sons, Ltd.]

B. FIGURE Idealized differential scanning calorimetry (DSC) or differential thermal analysis (DTA) thermogram: (A) temperature of glass transition, Tg; (B) crystallization; (C) crystalline melting point, Tm; (D) crosslinking; and (E) vaporization. dQ/dt = electrical power difference between sample and reference; T = difference in temperature between sample and reference. POLYMER CHEMISTRY

FIGURE 5.17. Differential thermal analysis (DTA) thermogram
of poly(vinyl chloride): (A) glass transition, Tg; (B) melting point; (c) oxidative attack; (D) dehydrochlorination; and (E) probable depolymerization. [From Matlack and Metzger,79 copyright 1966. reprinted by permission of John wiley & Sons, Inc.] POLYMER CHEMISTRY

Tg Tm A B Baseline 2 1 FIGURE Methods of reporting transition temperatures: (A) at the onset, and (B) at the inflection point or maximum, Tg= glass transition temperature; Tm= crystalline melting point.

5.6.2 Thermomechanical Analysis (TMA)
A. The method of TMA a. Using the probe sensing volume and modulus. b. Measuring volume change and modulus change during heating. c. Volume change : flat probe tip. Modulus change : tapered tip. d. Determining movement of the probe by variable transformer. e. TMA is more sensitive than DSC and DTA. B. Torsional braid analysis (TBA). a. Glass braid or thread is impregnated with the polymer sample. b. Determining torsional oscillation of braid and thread. POLYMER CHEMISTRY

5.6.3 Thermogravimetric Analysis (TGA).
A. TGA : Determining thermal stability of polymer. a. Determining weight loss as sample temperature is increased. b. Measuring weight loss by thermobalance. c. Determination environment : in air or in N2. B. Thermogram

5.6.3 Thermogravimetric Analysis (TGA).
C. Application a. Information of thermal stability : initial weight loss temperature, 10% weight loss temperature, 50% weight loss temperature. b. Polymer reactions by heating. 1) HCl from poly(vinyl chloride). 2) H2O from amic acid to make polyimide. D. Isothermal TGA : weight loss with time at a constant temperature. POLYMER CHEMISTRY

5.6.4 Pyrolysis-gas chromatography (PGC)
A. PGC : Pyrolysis device + GC column. B. Types of pyrolysis device. a. Furnace chamber pyrolysis : in the heated chamber. b. Flash pyrolysis : high-resistance coil or filament coated by polymer sample. c. laser pyrolysis : focused laser beam. C. Pyrogram.

FIGURE 5. 20. Pyrogram of high-density polyethylene
FIGURE Pyrogram of high-density polyethylene. Peaks correspond to (1) n-alkane, (2) 1-alkene, and (3) ,-alkadiene. Conditions: 25-m capillary column coated with poly(phenyl ether); pyrolysis 10 s at 1,000oC. [From Kolb et al.,89 courtesy of Springer-Verlag.]

5.6.5 Flammability Testing A. Limiting oxygen index (LOI).
a. The most versatile small-scale test. b. Minimum percentage of oxygen for burning. c. Burning condition : candlelike burning in three minutes. d. LOI = vol. O2 + vol. N2 vol. O2  100 POLYMER CHEMISTRY

5.6.5 Flammability Testing B. LOI test
FIGURE Schematic representation of the limiting oxygen index (LOI) test [Adapted from Fenimore and Martin.93] POLYMER CHEMISTRY

POLYMER CHEMISTRY

5.7 Measurement of Mechanical Properties.
A. Tensile strength, moldulus, elongation measurement. a. Size of specimen. b. Instrument : Instron 1) Loads weight range : few grams ~ 20,000 founds. 2) Measuring compressive and flexural strengths. ) To obtain stress-strain curve by this instrument. c. Fatigue 1) Alternative cycles of tensile and compressive stress. ) Fatigue resistance decreases as polymer rigidity or crosslinking increases POLYMER CHEMISTRY

a. Size of specimen. b. Instrument : Instron

a. Izod test : Striking weighted pendulum. b. Specimen size
B. Impact strength. a. Izod test : Striking weighted pendulum. b. Specimen size C. Hardness. a. Resistance to surface indentation. b. Indenting device : Spring-loaded needle-type indenter. D. Abrasion resistance. a. To measure weight loss by abrader or finely divided abrasive. E. Tear resistance. a. A weighted pendulum-mounted blade. b. Travel distance of pendulum. POLYMER CHEMISTRY

5.8 Evaluation of Chemical Resistance.
A. Resistance of chemical reagent. a. Immersing test samples in the chemical reagent (temperature and time). b. Measuring mechanical property change after immersing. c. Measuring retention of properties. d. Checking swelling, surface erosion, or crazing. e. Determining change in viscosity. POLYMER CHEMISTRY

5.8 Evaluation of Chemical Resistance.
B. Moisture resistance. a. Long-term exposure to water. C. Weatherability. a. Weathering chamber. 1) Humidity control. 2) Water spray. 3) UV lamps. POLYMER CHEMISTRY

5.9 Evaluation of Electrical Properties.
A. Resistivity measurement. a. Volume resistivity (ρv). E : the potential in volts. Iv : the measured dc current in amps. A : the area of the small electrode in square centimeters. t : the thickness in centimeters. b. Surface resistivity(ρs). I v: the current (amp). Dm : the mean diameter of the gap (cm). g : the width of the gap (cm). Rs : the resistance (ohm). v = Iv E t A = Rv A v = Is E g Dm = RsDm POLYMER CHEMISTRY

c. Unit of resistivity : ohm cm. 1) Insulator : above 108ohm cm 2) Semiconductor : ohm cm 3) Conductor : below 10-3 ohm cm d. Instrument POLYMER CHEMISTRY

B. Dielectric strength : Maximum voltage which sample can withstand. C. Dielectric constant : a measure of a samples contribution to the circuit capacitance. D. Arc resistance : the length of time before a high-voltage discharge arc POLYMER CHEMISTRY

Chapter 6. Free Radical Polymerization
6.1 Introduction 6.2 Free Radical Initiators. 6.3 Techniques of Free Radical Polymerization. 6.4 Kinetic and Mechanism of polymerization. 6.5 Stereochemistry of polymerization. 6.6 Polymerization of Dienes 6.7 Monomer Reactivity 6.8 Copolymerization. POLYMER CHEMISTRY

6. 1 Introduction A. Type of polymerization. polymerization
Addition polymerization Condensation polymerization Free-radical polymerization Ionic polymerization Complex coordination polymerization POLYMER CHEMISTRY

B. Commercialized free-radical polymerization.

6.2 Free Radical Initiators.
6.2.1 Peroxides and Hydroperoxides A. Benzoly peroxide and other peroxides a. Thermal decomposition of BPO. b. Half-life of benzoyloxy radical : 30 min at 100℃ c. Cage effect : confining effect of solvent molecules. POLYMER CHEMISTRY

6.2.1 Peroxides and Hydroperoxides
(6.5) d. Other peroxides. Diacetyl peroxide Di-t-butyl peroxide Diacetyl peroxide Di-t-butyl peroxide (half-life:10hours at 120℃) POLYMER CHEMISTRY

e. Promoters : Inducing initiation at lower temperature. (6.9) + - + (6.10) + POLYMER CHEMISTRY

B. Hydroperoxide a. Thermal decomposition hydroperoxide b. Cumyl hydroperoxide. POLYMER CHEMISTRY

6.2.2 Azo Compounds. A. α,α'-Azobis(isobutyronitrile) (AIBN).
A. α,α'-Azobis(isobutyronitrile) (AIBN). a. Decomposition of AIBN. b. Half-life of isobutyronitrile radical : 1.3 hours at 80℃. POLYMER CHEMISTRY

6.2.2 Azo Compounds. B. Side reaction : Cage effect.
a. Tetramethylsuccinonitrile b. Ketenimine POLYMER CHEMISTRY

6.2.3 Redox Initiators. A. One electron transfer reaction.
a. Making free radical by one electron transfer by redox reaction. b. Low-temperature reaction. c. Emulsion polymerization. B. Example of redox system. POLYMER CHEMISTRY

6.2.4 Photoinitiator A. Peroxide and Azo compound.
Photolysis and thermalysis. B. Photolabile initiator. POLYMER CHEMISTRY

· · 6.2.5 Thermal Polymerization. 10 12 11
A. Polymerization without initiators. a. Dimer formation by Diels-Alder reation. 10 b. Radical formation from dimer. POLYMER CHEMISTRY 11 12

6.2.6 Electrochemical Polymerization.
A. Polymerization of electrolysis. a. Cathode reaction : electron transfer to monomer ion forming radical anion (6.22) b. Anode reaction : electron transfer to anode forming radical cation (6.23) B. Coating metal surfaces with polymers. POLYMER CHEMISTRY

6.3 Techniques of Free Radical Polymerization.

6.3 Techniques of Free Radical Polymerization.
6.3.1 Bulk A. Reactor charges. a. Monomer. b. Initiator (soluble in monomer). B. Problems. a. Heat transfer. b. Viscosity. c. Auto-acceleration. POLYMER CHEMISTRY

6.3.2 Suspension. A. Reactor charges. a. Monomer.
b. Initiator (soluble in monomer). c. Water or other liquid. d. Stabilizer: Poly(vinyl alcohol), CMC B. Vigorously stirring to keep suspension. POLYMER CHEMISTRY

6.3.3 Solution. A. Reactor charges. a. Monomer (soluble in solvent).
a. Monomer (soluble in solvent). b. Initiator (soluble in solvent). c. Solvent. B. Refluxing solution. POLYMER CHEMISTRY

6.3.4 Emulsion. A. Reactor charges. a. Monomer. b. Redox initiator
a. Monomer. b. Redox initiator c. Soap or emulsifier. d. Water. e. Others (cf. Table 6.3). B. Polymerization in swollen micelle. Latex products. POLYMER CHEMISTRY

6.3.4 Emulsion. TABLE 6.3. Typical Emulsion Polymerization Recipesa
Styrene-Buradiene Copolymer Polyacrylate Latex Ingredients, Conditions Ingredients (parts by weight) Water Butadiene Styrene Ethyl acrylate 2-Chloroethyl vinyl ether p-Divinylbenzene Soap Potassium persulfate 1-Dodecanethiol Sodium pyrophosphate Conditions Time Temperature Yield 190 70 30 - 5 0.3 0.5 12hr 50oC 65% 133 - 93 5 2 3b 1 0.7 8hr 60oC 100% aRecipes from Cooper.23 bSodium lauryl sulfate.

6.4 Kinetic and Mechanism of polymerization.
A. Mechanism of free-radical polymerization. a. Initiation. 1) Decomposition. Initiator → 2R․ 2) Addition. (6.25) POLYMER CHEMISTRY

b. Propagation. (6.26) 1) Head-to-tail orientation : predominant reaction. Steric and electronic effects. 2) Examples of not exclusively head-to-tail orientation. (13-17% of head to head) (5-6% of head to head) (19% of head to head) POLYMER CHEMISTRY

c. Termination. 1) Combination. (6.27) Polystyrene radical. (6.29) POLYMER CHEMISTRY

2) Disproportionation. (6.28) Poly(methyl methacrylate) radical. (6.30) ① Repulsion of ester group. ② Easy alpha hydrogen abstraction. 3) Acrylonitrile : Combination virtually exclusively at 60℃. 4) Poly(vinyl acetate) : Disproportionation. POLYMER CHEMISTRY

B. Kinetic of free radical polymerization.
a. Assumption. 1) The rates of initiation, propagation, and termination are all different. 2) Independent of chain length. 3) Negligible end group. 4) At steady state, constant radical concentration. (steady state assumption) b. Initiation (Ri) f : Initiator efficiency. kd : Decomposition rate constant. [I] : molar concentration of initiator. [M ·] : molar concentration of radical. Ri = dt -d[M ·] = 2fkd[I] f = radicals formed from initiator radicals that initiate a polymer chain POLYMER CHEMISTRY

c. Termination rate ( Rt ) d. Propagation rate ( Rp ) Steady state assumption. Ri= dt -d[M·] = 2kt[M·]2 kt = ktc+ ktd Ri=Rt Rp = dt -d[M] = kp[M][M·] 2 Rp = dt -d[M] = kp[M] [M·]= POLYMER CHEMISTRY

e. Average kinetic chain length ( )   = Ri Rp = Rt  = 2kt[M·]2 kp[M][M·] = 2kt[M·] kp[M] Disproportionation : Combination : DP =  DP = 2 POLYMER CHEMISTRY

f. Gel effect : Trommsdorff effect, Norris-smith effect. 1) Difficult termination reaction because of viscosity. 2) Ease propagation reaction because monomer size is small, even though high viscosity. 3) Autoacceleration by exotherm of propagation reaction. 4) To obtain extraordinary high molecular weight polymer like gel. POLYMER CHEMISTRY

C. Chain transfer reactions : Growing radicals move to other parts
by hydrogen abstracting. Lowering average kinetic chain length. a. Growing radicals move to other polymer chain. (6.32) b. Backbiting self polymer chain. (6.33) POLYMER CHEMISTRY LDPE : branching polymer.

C. Chain transfer reactions
c. Moving to initiators or monomers. (6.34) (6.35) d. Moving to solvent. (6.36) (6.37) POLYMER CHEMISTRY

C. Chain transfer reactions
e. Moving to chain transfer agent. (6.39) tr 1 =  + [M} Ct : Chain transfer constant. [T] : Concentration of chain transfer agent. f. Telomerization : At high concentration of transfer agent, ktr>kp. Low-molecular-weight polymers are obtained. (Telomer) POLYMER CHEMISTRY

D. Leaving free radical polymerization : Atom transfer polymerization.
a. Copper(I) bypyridyl(bpy) complex: (6.42) (6.43) (6.44) b. TEMPO (18) : 2,2,6,6-tetramethylpiperidinyl-1-oxy. (6.45) POLYMER CHEMISTRY

c. Synthesis of block copolymers like anionic polymerization. d. Monodisperse polymerization (PI=1.05). E. Kinetics of Emulsion polymerization. a. N : the number of particles. b. POLYMER CHEMISTRY

6.5 Stereochemistry of polymerization.
A. General consideration. a. Stereoregular polymerization : Ionic and complex coordination polymerization. 1) Terminal ion pair : counter ion. 2) Terminal complex active site. 3) Low temperature. b. Stereo-irregular polymerization : Free-radical polymerization. 1) No stereoregulating radical terminal group. 2) Somewhat higher temperature. POLYMER CHEMISTRY

B. Factors influencing stereochemistry in free-radical polymerization. a. Interaction between the terminal chain carbon and the approaching monomer molecule. C. Stereoregular free-radical polymerization of PMMA. (syndiotatic PMMA) a. Polymerization temperature : below 0℃. b. (6.48) POLYMER CHEMISTRY

c. Terminal carbon : sp2( planar ) Penultimate repeating unit : Bulky ester group. d. Poly(2,4,6-triphenylbenzylmethacrylate) 19 1) Less syndiotatic than PMMA. 2) More polar effect than steric effect. POLYMER CHEMISTRY

6.6 Polymerization of Dienes
6.6.1 Isolated Dienes A. Crosslinked or cyclopolymerization. POLYMER CHEMISTRY

6.6.2 Conjugated Dienes. Isoprene 25
A. Structure of conjugated Diene monoer. Isoprene 23 B. a. 1,2-Addition : Pendent vinyl group. 25 b. Stereochemistry : isotactic, syndiotactic, atactic. POLYMER CHEMISTRY

6.6.2 Conjugated Dienes. C. 1,4-Addition : Delocalized double bond a.
a. 24 26 27 D. 3,4-Addition 29 POLYMER CHEMISTRY E. Polymerization reaction and temperature.

6.6.2 Conjugated Dienes. TABLE 6.6 Structure of Free Radical-Initiated Diene Polymersa Percent polymerization Temperature (oC) -20 20 100 233 -5 50 257 -46 46 Monomer Butadiene Isoprene Chloroprene cis-1, trans-1, , ,4 6 22 28 43 1 7 18 23 12 5 10 13 77 58 51 39 90 82 72 66 94 81-86 71 17 20 21 18 5 2 1 2.4 - 4 5 6 9 0.3 1 2.4 aData from Cooper34 p. 275.

6.6.2 Conjugated Dienes. F. s-cis and s-trans POLYMER CHEMISTRY

6.7 Monomer Reactivity A. Thermodynamic feasibility.
a. ΔGp = ΔHp - TΔSp ΔGp : Gibbs free energy change of polymerization. ΔHp : Enthalpy change of polymerization. ΔSp : Entropy change of polymerization. ΔGp < 0 : favorable free energy of polymerization. b. Values of ΔH and ΔS for several monomers. c. Polypropylene and isobutylene : ΔG < 0 → unfavorable polymerization. because of kinetic feasibility POLYMER CHEMISTRY

6.7 Monomer Reactivity TABLE 6.7. Representative Enthalpies, H, and
POLYMER CHEMISTRY TABLE 6.7. Representative Enthalpies, H, and Entropies, S, of Polymerizationa Monomer Acrylonitrileb 1,3-Butadiene Ethylene Isoprene Methyl methacrylate Propylene Styrene Tetrafluoroethylene Vinyl acetate Vinyl chloride 77 78 109 75 65 84 70 163 90 71 -H (kJ/mol) -S (J/mol) 89 155 101 117 116 104 - aValues selected from Ivin.29c Polymerization temperature 25oC unless otherwise indicated. b74.5oC. c127oC.

6.7 Monomer Reactivity B. Factors of monomer reactivity in free radical polymerization. a. The stability of the monomer toward addition of a free radical. b. The stability of the monomer radicals. c. Order of monomer reactivity. Acrylonitrile > Styrene > Vinyl acetate. d. Order of benzoyloxy radical initiation. Syrene > Vinyl acetate > Acrylonitrile Benzoyloxy radical : Ph14CO2․ POLYMER CHEMISTRY

6.7 Monomer Reactivity C. The inverse relationship between monomer stability and polymerization rate. a. Vinyl acetate: not Stable monomer but high rate constant. b. Steric and polar effects: Not clear-cut generalization. Lower rate constant of MMA than MA. c. 1,2 disubstituted monomer difficult to polymerize in free radical. Exception: Tetrafluoroethylene. POLYMER CHEMISTRY

6.7 Monomer Reactivity D. Ceiling temperature (Tc) a.
a. b. Definition of ceiling temperature. ΔGp = 0 : equal forward and backword reactions. c. High Tc : favorable polymerization. Low Tc : unfavorable polymerization. Exception : α-methylstyrene (Tc=66℃). POLYMER CHEMISTRY

6.8 Copolymerization. A. Mechanism of copolymerization.
POLYMER CHEMISTRY

B. Kinetics of copolymerization.
b. c. let, (reactivity ratio) steady state assumption. d. solving : Copolymer equation or copolymer composition equation. d[M1]/d[M2] : the molar ratio of the two monomers in the copolymer [M1], [M2] : the initial molar concentration of monomers in the reaction mixture and

C. Significance of reactivity ratio (r1, r2).
a. r1 = r2 = ∞ : Homopolymer. b. r1 = r2 = 0 : Alternating polymer. c. r1 = r2 = 1 : Copolymer composition depending on feeding monomers in the reaction temperature. d. r1 × r2 = 1 :Ideal copolymerization like ideal liquid vaporization. e. r1 × r2 > 1 : Azotropic copolymerization (polymer composition not depending on feeding). f. Determination of r1, r2 : Measure copolymer composition by NMR or other method at low conversion ( <10% ) POLYMER CHEMISTRY

D. Alfrey-price Q-e scheme.
b. c. For styrene Q=1.0 , e=-0.8 d. Q : resonance stabilization. e : less negative values equal more electron attracting. POLYMER CHEMISTRY

E. Charge transfer complex polymerization(alternating copolymer).
a. Styrene and maleic anhydride(D-A complex). + -  (6.54) POLYMER CHEMISTRY

E. Charge transfer complex polymerization (alternating copolymer).
b. (6.57) c. (6.58) POLYMER CHEMISTRY

Chapter 7. Ionic polymerization
7.1 Introduction 7.2 Cationic polymerization 7.3 Anionic polymerization 7.4 Group transfer polymerization

more complex than free radical polymerizations but more versatile
7.1 Introduction Presence of counterions (= gegenions) Influence of counterions Solvation effect more complex than free radical polymerizations but more versatile ex) counterion

7.1 Introduction Application : in ring-opening polymerizations of cyclic ethers , lactams , lactones and in the polymerization of aldehydes , ketones Commercial processes (Table 7.1) far fewer in number reflect a much narrower choice of monomers monomers must contain substituent groups capable of stabilizing carbocations or carbanions the necessity for solution polymerzation

TABLE 7.1. Commercially Important Polymers Prepared by Ionic Polymerization
Polymer or Copolymer Major Uses Cationica Polyisobutylene and polybuteneb (low and high molecular weight) Isobutylene-isoprene copolymerc (“butyl rubber”) Isobutylene-cyclopentadiene copolymer Hydrocarbond and polyterpene resins Coumarone-indene resinse Poly(vinyl ether)s Anionicf cis-1,4-Polybutadiene cis-1,4-Polisoprene Styrene-butadiene rubber (SBR)g Styrene-butadiene block and star copolymers ABA block copolymers (A= styrene, B=butadiene or isoprene) polycyanoacrylateh Adhesives, sealants, insulating oils, lubricating oil and grease additives, moisture barriers Inner tubes, engine mounts and springs, chemical tank linings, protective clothing, hoses, gaskets, electrical insulation Ozone-resistant rubber Inks, varnishes, paints, adhesives, sealants Flooring, coatings, adhesives Polymer modifiers, tackifiers, adhesives Tires Tires, footware, adhesives, coated fabrics Tire treads, belting, hose, shoe soles, flooring, coated fabrics Flooring, shoe soles, artificial leather, wire and cable Thermoplastic elastomers Adhesives aAlCl3 and BF3 most frequently used coinitiators. b”Polybutenes” are copolymers based on C4 alkenes and lesser amounts of propylene and C5 and higher alkenes from refinery streams. cTerpolymers of isobutylene, isoprene, and divinylbenzene are also used in sealant and adhesive formulations. dAliphatic and aromatic refinery products. eCoumarone (benzofuran) and indene (benzocyclopentadiene) are products of coal tar. fn-Butyllithium most common initiator. gContains higher cis content than SBR prepared by free radical polymerization. hMonomer polymerized by adventitious water.

7.2 Cationic polymerization
7.2.1 Cationic initiators 7.2.2 Mechanism, kinetics, and reactivity in cationic polymerization 7.2.3 Stereochemistry of cationic polymerization 7.2.4.Cationic copolymerization 7.2.5 Isomerization in cationic polymerization

7.2.1 Cationic Initiators The propagating species : carbocation
Initiation + (7.1) Initiator mineral acid : H2SO4, H3PO4 lewis acid : AlCl3, BF3, TiCl4, SnCl4 Coinitiator

7.2.1 Cationic Initiators (7.5) (7.6) (7.7) (7.8)
Very active Lewis acid autoionization Other initiators (7.5) (7.6) (7.7) (7.8)

7.2.1 Cationic Initiators Other initiators + - (7.9) (7.10)

(Markovnikov’s rule) intermediate is formed.
7.2.2 Mechanism, Kinetics, and Reactivity in Cationic Polymerization Carbocationic Initiation. addition of the electrophilic species – the more stable carbocation (Markovnikov’s rule) intermediate is formed. Stability of carbocation

(Because of steric hindrance)
7.2.2 Mechanism, Kinetics, and Reactivity in Cationic Polymerization Carbocationic Initiation. For a series of para-substituted styrenes, the reactivity for substituent group Vinyl ethers (7.11) X (Because of steric hindrance)

① -complex of chain end and approaching monomer
7.2.2 Mechanism, Kinetics, and Reactivity in Cationic Polymerization B. Propagation Step Two Step ① -complex of chain end and approaching monomer ② formation of covalent bond ① ② (7.12)

favors the initiation step)
7.2.2 Mechanism, Kinetics, and Reactivity in Cationic Polymerization C. Influences polymerization rate Covalent Intimate ion pair Solvent-separated Solvated ions (7.13) ① Solvent polarity (polarity ② Degree of association between the cationic chain end and counterion (A-) favors the initiation step)

7.2.2 Mechanism, Kinetics, and Reactivity in Cationic Polymerization
D. Chain transfer reaction 1. With monomer : 2. By ring alkylation (7.14) (7.15)

D. Chain transfer reaction 3. By hydride abstraction from the chain to form a more stable ion : 4. With solvent-for example, benzene-by electrophilic substitution : (7.16) (7.17)

initiator ① styrene + CF3COOH (7.18) ② Isobutylene + BCl3/H2o (7.19)
7.2.2 Mechanism, Kinetics, and Reactivity in Cationic Polymerization E. Termination reaction Termination are the combination of chain end with counterion. (7.18) (7.19) ① styrene + CF3COOH initiator ② Isobutylene + BCl3/H2o

A:proton trap·· B:monomer·· A B (7.20)
7.2.2 Mechanism, Kinetics, and Reactivity in Cationic Polymerization F. Proton trap It intercepts the proton before it transfers to monomer. The result lower overall yield higher molecular weight lower polydispersity index. (7.20) A:proton trap·· B:monomer·· A B

G. Telechelic Polymer (7.21) (7.22) (7.23) inifer (bifunctional compound)

H. Pseudocationic Polymerization (7.24) The reaction proceeds at a much slower compared with most cationic processes. The propagating chain end is a covalently bonded perchlorate ester

① formation of tertiary carbocation-initiating species.
7.2.2 Mechanism, Kinetics, and Reactivity in Cationic Polymerization I. To prepare living polymers under cationic conditions. Tertiary ester + BCl3 / Isobutylene polymerization ① formation of tertiary carbocation-initiating species. ② Polymerization to yield polyisobutylene terminated (7.27)  – … (7.26) : appearance of a very tightly bound – but still active – ion pair (Termination or chain transfer reaction 없이 중합반응이 종결되는 예) ex1)

(Termination or chain transfer reaction 없이 중합반응이 종결되는 예)
7.2.2 Mechanism, Kinetics, and Reactivity in Cationic Polymerization I. To prepare living polymers under cationic conditions. I2 / HI or I2 / ZnI2 : vinyl ether propagation (7.27) Living Polymer Termination이 전체적으로 멈춘 곳에서 chain end가 여전히 active 한 성질을 가지고 있는 polymer Monomer 첨가 시 분자량이 증가하며 starting monomer와 다를 경우 block copolymer형성 매우 길고 anionic polymerization에 많이 이용 대부분의 living polymer는 낮은 온도에서 합성 Living polymer란 용어는 정지 반응이 일어나지 않는 이온 중합에 이용 ex2) (Termination or chain transfer reaction 없이 중합반응이 종결되는 예)

J. Kinetics Expression of general initiation, propagation, termination, and transfer rates : molar concentration of initiation : molar concentration of monomer : molar concentration of cationic chain end As with free radical polymerization approximation to a steady state for the growing chain end. or thus

TABLE 7.2. Representative Cationic propagation Rate Constants,
7.2.2 Mechanism, Kinetics, and Reactivity in Cationic Polymerization TABLE 7.2. Representative Cationic propagation Rate Constants, Monomer Styrene -Methylstyrene i-Butyl vinyl ether Methyl vinyl ether 2-Chloroethyl vinyl ether Solvent None CH2Cl2 Temperature (oC) 15 30 Initiator Radiation C7H7+SbCl6- kp (L/mol s) 3.5  106 4  106 3  105 5  103 3.5  103 1.4  102 2  102 aData from Ledwith and Sherrington.19

Substituting for in , one obtains In the absence of any chain transfer, (the kinetic chain length = ) = If transfer is the predominant mechanism controlling chain growth,

free radical process cationic process
7.2.2 Mechanism, Kinetics, and Reactivity in Cationic Polymerization K. Difference between free radical and cationic processes. free radical process cationic process propagation rate (Rp) DP () proportional to the square root of initiator concentration dependent of initiator concentration first-order dependence independent of initiator concentration

L. Nonconjugation diene – Cationic cyclopolymerization (7.28)

7.2.3 Stereochemistry of Cationic Polymerization
lead to stereoregular structures. ex) vinyl ether  - methylstyrene Vinyl ether observation resulting greater stereoregularity is achieved at lower temperatures the degree of stereoregularity can vary with initiator the degree and type of stereoregularity (isotactic or syndiotactic) vary with solvent polarity.

Solvent effect EX) t-butyl vinyl ether forms isotactic polymer in nonpolar solvents. forms mainly syndiotactic polymer in polar solvents. ( cationic chain end and the counterion are associated )

Solvent effect In polar solvents both ions 1) be strongly solvated 2) the chain end – exist as a free carbocation surrounded by solvent molecules In nonpolar solvents 1) association between carbocation chain end and counterion would be strong 2) counterion could influence the course of steric control.

Models proposed for vinyl ether polymerization
(7.29) (7.30)

(7.31) (7.32) (7.33)

7.2.4 Cationic Copolymerization
A. Copolymerization equation - the situation is complication by counterion effects. B. Reactivity ratios vary with initiator type and solvent polarity. C. Temperature – unpredictable effect D. Steric effects (Table 7.3) E. commercial cationic copolymers – butyl rubber (prepared from isobutylene and isoprene.) protective clothing tire inner tubes

TABLE 7.3. Representative Cationic Reactivity Rations (r)a
Temperature (oC) Monomer 1 Monomer 2 Coinitiatorb Solventb r1 r2 Isobutylene Styrene p-Chlorostyrene Ethyl vinyl ether 2-Chloroethyl vinyl ether 1,3-Butadiene Isoprene Cyclopentadiene Styrene -Methylstyrene p-Methylstyrene trans--Methyl- styrene cis--Methyl- i-Butyl vinyl ether AlEtCl2 AlCl3 BF3·OEt2 SnCl4 TiCl4 BF3 CH3Cl PhCH3 EtCl CCl4 CH2Cl2 CCl4/PhNO2(1:1) -100 -103 -78 -92 -23 43 115 2.5 0.60 1.60 9.02 1.2 0.05 0.33 1.80 1.0 0.74 1.30 6.02 0.4 4.5 1.17 1.99 5.5 2.90 1.74 1.10 0.32 0.92 0.42 aData from Kennedy and Marechal.5 bEt = C2H5, Ph = phenyl.

7.2.5 Isomerization in Cationic Polymerization
(7.34) (7.35)

7.3 Anionic Polymerization
Anionic initiators Mechanism, kinetics, and reactivity in anionic polymerization Stereochemistry of anionic polymerization Anionic copolymerization

Monomers having substituent group – stabilizing a carbanion
7.3.1 Anionic Initiators Propagating chain - carbanion (7.36) Monomers having substituent group – stabilizing a carbanion resonance or induction Examples – nitro, cyano, carboxyl, vinyl, and phenyl.

7.3.1 Anionic Initiators (7.37) high reactivity (7.38)
The strength of the base necessary to initiate polymerization depends in large measure on monomer structure (7.37) high reactivity (7.38) cyanoacrylate adhesives

7.3.1 Anionic Initiators Two basic types
that react by addition of a negative ion that undergo electron transfer. ① The most common initiators that react by addition of a negative ion simple organometallic compounds of the alkali metals For example : butyllithium Character of organolithium compounds - low melting - soluble in inert organic solvents. Organometallic compounds of the higher alkali metals - more ionic character - generally insoluble

Electron transfer processes (involving metal donor D· , monomer M)
7.3.1 Anionic Initiators ② Electron transfer (charge transfer) by free alkali metal : solutions in liquid ammonia or ether solvents suspensions in inert solvents by addition complex of alkali metal and unsaturated or aromatic compounds. Electron transfer processes (involving metal donor D· , monomer M)

7.3.2 Mechanism, kinetics, and reactivity in anionic polymerization
A. Mechanism을 변화시킬 수 있는 요인 a. solvent polarity ion pair solvent separated ion pair solvated ion Degree of association of ion counterion의 역할 polar solvent : solvated ion 우세 non polar solvent : 이온들간의 association우세  - complex형성

b. Type of cation (counterion) c. Temperature B. The rate of initiation - initiator 와 monomer의 structure에 의존 C. Initiation by electron transfer dianion 생성 (7.46) (7.47)

D. Kinetic Because the second step is slow relative to the first, Chain termination is known to result primarily by transfer to solvent: Rate expressions for propagation and transfer may be written in the conventional way:

D. Kinetic Assuming a steady state whereby and Substituting in Rp we obtain The average kinetic chain length, is expressed as

E. Other types of transfer reactions

living anionic polymers can be made When impurities are rigorously excluded When the polymerization temperature is kept low In Living Polymerization F. all chains begin to grow simultaneously. No termination, no chain transfer reaction. as monomer is completely consumed. electron transfer initiators

G. Important factor in propagation rate. a. Association between counterion and terminal carbanion (7.54) TABLE 7.4. Representative Anionic Propagation Rate Constants, kp, for Polystyrenea Counterion Solvent kp (L/mol s)b Na+ Li+ Tetrahydrofuran 1,2-Dimethoxyethane Benzene Cyclohexane 80 3600 160 c (5-100)10-5c aData from Morton.30 Bat 25oC unless otherwise noted. cVariable temperature.

G. Important factor in propagation rate. b. Monomer structure steric effect inductive destabilization of the carbanion

7.3.3 Stereochemistry of anionic polymerization
A. Stereochemical of nondiene vinyl monomer With soluble anionic initiators (homogeneous conditions) at low temperatures, polar solvents favor syndiotactic placement nonpolar solvents favor isotactic placement. (stereochemistry depends in large measure on the degree of association with counterion, as it does in cationic polymerization) (7.55)

A. Stereochemical of nondiene vinyl monomer (7.56)

A. Stereochemical of nondiene vinyl monomer Effect of solvent (a) (b) SCHEME 7.1. (a) Isotactic approach of methyl methacrylate in a nonpolar solvent(b) Syndiotactic approach of methyl methacrylate in tetrahydrofuran.(Circles represent backbone or incipient backbone carbons: R=methyl. Backbone hydrogens omitted.)

B. Stereochemical of Dienes isoprene 1,3-butadiene catalyst, solvent의 영향 Li-based initiator/nonpolar solvents cis-1,4 polymer의 생성이 증가 ex) Isoprene/BuLi/pentane or hexane cis-1,4 polyisoprene

formation of cis-polyisoprene – lithium’s ability s-cis comformation by pi complexation – hold isoprene (7.57) forming a six-membered ring transition state – “lock” the isoprene into a cis-configuration (7.58) (7.59) steric effect

7.3.4 Anionic Copolymerization
Complicating factors of counterion. ① solvating polar of the solvent ② temperature effect ③ electron transfer initiator 사용 Table 7.5 free radical polymerization Anionic polymerization competition (7.60) ④ contrasts between homogeneous and heterogeneous polymerization systems. relatively few reactivity ratios

TABLE 7.5. Representative Anionic Reactivity Ratios (r)a
Monomer 1 Monomer 2 Initiatorb Solventc Temperatured (oC) r1 r2 Na n-BuLi EtNa RLi NaNH2 NH3 None Hexane THF Benzene Cyclohexane 25 50 -78 40 0.12 e 0.04 0.03 4.0 11.0 0.96 0.046 0.01 3.38 0.25 0.34 3.2 6.4 11.2 12.5 11.8 0.3 0.4 1.6 16.6 0.47 7.9 6.7 Methyl methacrylate Butadiene Isoprene Acrylonitrile Vinyl acetate Styrene aData from Morton.30 bBu=butyl, Et=ethyl, R=alkyl. cTHF=tetrahydrofuran. dTemperature cot specified in some instances. eNo detectable styrene in polymer.

formation of block copolymers by the living polymer method. (7.61)

Commercial block copolymers ABA triblock polymers – Greatest commercial success ex) styrene-butadiene-styrene (7.62) star-block (radial) – much lower melt viscosities, even at very high molecular weights ex) silicon tetrachloride (7.63)

7.4 Group Transfer Polymerization (GTP)
(In the 1980s a new method for polymerizing acrylic-type monomers) GTP의 특성 ① Anionic polymerization에서 흔히 사용되는 monomer를 사용 Living polymer로 전환 ② Propagating chain Covalent character ③ Organosilicon이 개시제로 사용 (7.64) living polymer Organosilicon에서 SiR3가 transfer되어 중합을 형성(GTP)

N,N-Dimethylacetamide N,N-Dimethylformamide Ethyl acetate
TABLE 7.6. Representative Compounds Used in Group Transfer Polymerization Monomersa Initiatorsa Catalystsa Solvents Anionicb Acetonitrile 1,2-Dichloroethaned Dichloromethaned N,N-Dimethylacetamide N,N-Dimethylformamide Ethyl acetate Propylene carbonate Tetrahydrofuran Toluened aR=alkyl, Ar=aryl, Me=methyl, X=halogen. b0.1 mol% relative to initiator. c10-20 mol% relative to monomer. dPreferred with Lewis acid catalysts.

* Synthesis of initiator 두 개의 작용기를 갖는 개시제 사용 사슬의 양끝에서 성장 (7.65)

(7.66) (7.67) Speciality ① Once the monomer is consumed, a different monomer may be added ② chain can be terminated by removal of catalyst. ③ chain can be terminated by removal by protonation or alkylation.

GPT mecahanism (7.68)

(7.69) Chain transfer of GPT

8.1 Introduction 8.2 Heterogeneous Ziegler-Natta polymerization 8.3 Homogeneous Ziegler-Natta polymerization 8.4 Ziegler-Natta copolymerization 8.5 Supported metal oxide catalysts 8.6 Alfin catalysts 8.7 Metathesis polymerization

at low temperatures and pressures
8.1 Introduction Karl Ziegler’s discovery ( in Germany-1950s) at low temperatures and pressures transition metal compound (Ti, V, Cr) + ethylene을 중합 Organometallic compound (AlR3) linear polyethylene (HDPE) – denser, tougher, higher melting because the more regular structure allows closer chain packing and a high degree of crystallinity. HDPE (high-density polyethylene) – bottle, pipe LDPE (low-density polyethylene) – lap, film, coating LLDPE (linear low-density polyethylene) - copolymer of ethylene and 1-butene (Ziegler-type catalysts) - less energy to produce than LDPE

8.1 Introduction (Ziegler & Natta - 1963년 Nobel Prize)
Giulio Natta’s discovery ( in Italy) polymerizing  - olefins (1-alkenes) + catalysts of the type described by Ziegler Stereoregularity polymer 생성. (Ziegler & Natta - 1963년 Nobel Prize) Reduced Metal Oxides Alfin catalyst Other complex catalysts.

Principal Stereochemistry
TABLE 8.1 Commercially Available Polymers Synthesized with Complex coordination Catalysts Polymer Principal Stereochemistry Typical Uses Plastics Polyethylene, high density (HDPE) Polyethylene, ultrahigh molecular weight (UHMWPE) Polypropylene Poly(1-butene) Poly(4-methyl-1- pentene)a Polystyrene 1,4-Polybutadiene 1,4-Polyisoprene Ethylene-1-alkeneb copolymer (linear low- density polyethylene, LLDPE) Ethylene-propylene block copolymers (polyallomers) Polydicyclopentadienec Bottles, drums, pipe, conduit, sheet, film, wire and cable insulation Surgical prostheses, machine parts, heavy, heavy-duty liners Automobile and appliance parts, rope, cordage, webbing, carpeting film Film, pipe Packaging, medical supplies, lighting Specialty plastics Metal cam coatings, potting compounds for transformers Golf ball covers, orthopedic devices Blending with LDPE, packaging film, Bottles Food packaging, automotive trim, toys, bottles, film, heat-sterilizable containers Reaction injection molding (RIM) structural plastics - Isotactic Syndiotactic trans

Principal Stereochemistry cis trans -
TABLE 8.1 Commercially Available Polymers Synthesized with Complex coordination Catalysts Polymer Principal Stereochemistry Typical Uses Tires, conveyer belts, wire and cable insulation, footware Tires, footware, adhesives, coated fabrics Blending with other elastomers Molding compounds, engine mounts, car bumper guards Asphalt blends, sealants, adhesives, cable coatings Impact modifier for polypropylene, Wire and cable insulation, weather stripping, tire side walls, hose, seals cis trans - Elastomers 1,4-Polybutadiene 1,4-Polyisoprene Poly(1-octenylene) (polyoctenamer)c Poly(1,3-cyclo- pentenylene polymer)c Polypropylene (amorphous) Ethylene-propylene copolymer (EPM, EPR) Ethylene-propylene- diene copolymer (EPDM) aUsully copolymerized with small amounts of 1-pentene. b1-Butene, 1-hexene, and 1-octene. cSynthesized by ring-opening metathesis polymerization of the corresponding cycloaldene.

8.2 Heterogenous Ziegler-Natta Polymerization
8.2.1 Heterogeneous Catalysts Definition (1) transition metal compound ( an element from groups Ⅳ to Ⅷ ) - catalyst - halides or oxyhalides of Ti, V, Cr, Mo, Zr (2) organometallic compound ( a metal from groups Ⅰ to Ⅲ ) - cocatalyst - hydrides, alkyls, or aryls of metals (such as Al, Li, Zn, Sn, Cd, Be, Mg) Most important from the commercial standpoint TiCl3 TiCl4 + R3Al combination of

8.2.1 Heterogeneous Catalysts Catalyst preparation mixing the components in a dry inert solvent in the absence of oxygen usually at a low temperature. Character of Catalysts having high reactivity toward many nonpolar monomers. high degree of stereoregularity.

8.2.1 Heterogeneous Catalysts TiCl4-AlR3 (R = alkyl) system – initially exchange reactions (8.1) (8.2) (8.3) then reduction via homolytic bond cleavage (8.4) (8.5)

8.2.1 Heterogeneous Catalysts Remove of radicals formed in these reactions by combination, disproportionation, or reaction with solvent. TiCl3 – formation by the equilibrium (8.8)

8.2.1 Heterogeneous Catalysts Stereochemistry에 영향을 미치는 요인 Better activity is by using TiCl3 TiCl3의 , , ,  form , ,  : high degree of stereoregularity  : 40%-50% stereoregularity, 50%-60% – linear structure (atactic polymer) close-packed layered crystal structures. stereoregularity is very much dependent on surface characteristics of the catalyst. The nature of the transition metal The alkyl groups of the cocatalyst The presence of additives.

TABLE 8.2. Variation of Polypropylene Isotacticity with Catalysta
Catalystb Stereoregularity (%) AlEt3 + TiCl4 AlEt3 + -TiCl3 AlEt3 + -TiCl3 AlEt3 + ZrCl4 AlEt3 + VCl3 AlEt3 + TiCl4 + P, As, or SB compounds AlEt2X + TiCl3 AlEtX2 + -TiCl3 + amine 35 45 85 55 73 90-99 99 a Data from Jordan6 and Dawans and Teyssié.7 b Et = ethyl; X = halogen.

8.2.1 Heterogeneous Catalysts Problem of Ziegler-Natta catalysts low efficiency difficult of catalyst remove improvement of low efficiency (high-mileage catalysts) Impregnating the catalyst on a solid support (MgCl2, MgO) Ex) typical TiCl3-AlR3 catalyst yields about g/atm,h,g(catalyst) of polyethylene using a MaCl2-supported catalyst – 7000g/atm,h,g(catalyst) Activity

a) monometallic mechanism
Mechanism and Reactivity in Hetrerogeneous Polymerization A. Two mechanism a) monometallic mechanism ① Monomer is complexed at a titanium atom exposed on the catalyst surface by a missing chlorine atom. ② Shifting the vacant octahedral position ③ Insertion reaction ④ Migration of the chain occurs to reestablish the vacant site on the surface. SCHEME 8.1

SCHEME 8.1. Monometallic mechanism of Ziegler-Natta polymerization.

a) Bimetallic mechanism
Mechanism and Reactivity in Heterogeneous Polymerization A. Two mechanism a) Bimetallic mechanism Ti 와 monomer가 -complex를 이룬다. Cyclic transition state가 존재한다. Ionization Original form 두 mechanism의 공통점 ① Ti atom과 monomer가 -complex를 이룬다. ② Cyclic transition state가 존재한다. ③ Insertion에 의해 중합반응이 진행된다. (stereoregularity 결점)

SCHEME 8.2. Bimetallic mechanism of Ziegler-Natta polymerization.

Ziegler-Natta polymerization – nonpolar monomers사용
Mechanism and Reactivity in Heterogeneous Polymerization Ziegler-Natta polymerization – nonpolar monomers사용 monomer activity – decreases with increasing steric hindrance about the double bond. reactivity

transfer to monomer (8.9 and 8.10) internal hydride transfer (8.11)
Mechanism and Reactivity in Heterogeneous Polymerization Termination transfer to monomer (8.9 and 8.10) internal hydride transfer (8.11) transfer to cocatalyst or to an added alkylmetal compound (8.12) transfer to added hydrogen (8.13) (8.9) (8.10) (8.11) (8.12) (8.13)

Hydrogen – the preferred transfer agent
Mechanism and Reactivity in Heterogeneous Polymerization (8.14) Hydrogen – the preferred transfer agent because it reacts cleanly, leaves no residue low in cost Molecular weight distributions insoluble catalyst - broad soluble catalyst - narrower

A B Polymerization C rate Time
Mechanism and Reactivity in Heterogeneous Polymerization FIGURE 8.1 Types of rate curves observed in Ziegler-Natta polymerization: (A) constant; (B) decaying; and (C) decaying to constant. Polymerization rate Time A B C

8.2.3 Stereochemistry of Heterogeneous Polymerization
insoluble catalysts Isotactic polymers level of stereoregularity – depending, to a degree, on how exposed the active site is on the catalyst surface. 1-alkenes – approaches from the same side, giving rise to isotactic placement. double bond of the monomer undergoes cis opening exclusively cis addition to the double bond occurs

Similar behavior : 1,2-disubstituted olefins.
Stereochemistry of Heterogeneous Polymerization erythro-Diisotactic threo-Diisotactic (8.15) (8.16) Similar behavior : 1,2-disubstituted olefins.

8.2.4 Polymerization of Dienes
1,3-butadiene : the four possible structures cis-1,4 ; trans-1,4 ; isotatic 1,2 ; syndiotactic 1,2 TABLE 8.3. Catalysts for the Stereospecific Polymerization of Butadiene Catalysta Yield (%) Polymer structureb Ref. no. R3Al + VCl4 R3Al + VCl3 R3Al + VOCl3 R3Al + TiI4 R2AlCl + CoCl2 R3Al + Ti(OC6H9)4 Et3Al + Cr(C6H5CN)6 Al/Cr = 2 Al/Cr = 10 97-98 99 93-94 96-97 90-100 ~100 trans-1,4 cis-1,4 1,2 st-1,2 it-1,2 2 13 14 a Et = ethyl b st = syndiotactic, it = isotactic.

Catalysta Yield (%) Polymer Structure Ref. No. R3Al + -TiClB3
8.2.4 Polymerization of Dienes Isoprene cis- and trans-1,4, 1,2, and 3,4 polymerization TABLE 8.4. Catalysts for the Stereospecific Polymerization of Isoprene Catalysta Yield (%) Polymer Structure Ref. No. R3Al + -TiClB3 Et3Al + VCl3 Et3Al + TiCl4 Al/Ti < 1 Al/Ti > 1 Et3Al + Ti(OR)4 91 99 95 96 trans-1,4 cis-1,4 3,4 15 14 a Et = ethyl

Definition of mechanism
8.2.4 Polymerization of Dienes Definition of mechanism whether the catalyst coordinates one(1,2 polymerization) or both(1,4 polymerization) double bonds of the diene. 2. that coordination of a -allylic structure occurs and that the direction of approach of monomer determines the structure. (8.17) (8.18)

Conjugated cyclic dienes : Ziegler-Natta polymerization
8.2.4 Polymerization of Dienes (8.19) (8.20) Conjugated cyclic dienes : Ziegler-Natta polymerization Nonconjugated dienes : coordination catalysts 1 2

8.3 Homogeneous Ziegler-Natta Polymerization
8.3.1 Metallocene Catalysts Cp2TiCl2 3 R2AlCl 4 5 6 The earliest metallocene catalysts MAO – used in conjunction with metallocene catalysts

8.3.1 Metallocene Catalysts General structure Examples of catalysts 7 M : Zr, Ti, Hf X : Cl, alkyl Z : C(CH3)2, Si(CH3)2, CH2CH2 R : H, alkyl 9 8 Me2Si(Ind)2ZrCl2 Me2C(Flu)(Cp)ZrCl2 form isotactic and syndiotactic polypropylene usually written in condensed form

8.3.2 Mechanism and Reactivity with Metallocene Catalysts Difference between metallocene and heterogeneous Ziegler-Natta catalysts ① the former have well-defined molecular structure ② polymerization occurs at one position in the molecule ③ the transition metal atom. SCHEME Formation of the active site in a zirconocene catalyst. 10 3

8.3.2 Mechanism and Reactivity with Metallocene Catalysts SCHEME 8.4. Possible polymerization mechanism for ethylene.

8.3.2 Mechanism and Reactivity with Metallocene Catalysts Character of polymers prepared with metallocene catalysts ① Narrower molecular weight distributions than those prepared with heterogeneous catalysts. Better mechanical properties. ③ Polydispersities (Mw/Mn) range from 2to 2.5 for the former, compared with 5 to 6 for the latter. ④ The molecular weight of the metallocene-based polymers decreases with increasing polymerization temperature, increasing catalyst concentration, and addition of hydrogen to the monomer feed.

8.3.2 Mechanism and Reactivity with Metallocene Catalysts Activities of metallocene catalysts from 10 to 100 times higher than those of conventional Ziegler-Natta catalysts. While it is often difficult to correlate structural variables with activity, the following generalizations can be made : For the group 4B metals, the order of activity is Zr>Ti>Hf. Alkyl groups on the cyclopentadiene rings increase catalyst activity if they are not too bulky. Large, bulky alkyl groups and electron-withdrawing groups decrease the activity. Increasing the size of the groups attached to the atom bridging the cyclopentadiene rings (C or Si) reduces the activity. MAO affords much higher catalyst activities than ethyl- or higher alkylalumoxane cocatalysts.

8.3.2 Mechanism and Reactivity with Metallocene Catalysts Another way that metallocene catalysts differ from eterogeneous catalysts 11 (8.21) norbornene high-melting stereoregular polymers

8.3.3 Stereochemistry of Metallocene-Catalyzed Polymerization Metallocene catalysts exhibit a remarkable ability to control polymer stereochemistry. Structural variations synthesis of atactic polypropylene and higher poly(1-alkenes) isotactic syndiotatic type CpZrCl2 atactic polymer isotactic and syndiotactic polymer 8 9 chiral achiral

8.3.3 Stereochemistry of Metallocene-Catalyzed Polymerization The much different sizes of the two pi ligands of 8 assumed to play a role in the formation of symdiotactic polymer substitution of a methyl group on the cyclopentadiene ring of 9 hemiisotactic polypropylene (alternate methyls isotactic, the others atactic)

8.3.3 Stereochemistry of Metallocene-Catalyzed Polymerization Producing polypropylene having alternating atactic and isotactic blocks Ex) The zirconium catalyst can rotate between chiral and achiral geometries 12 (8.22) Thermoplastic elastomers having a range of properties from a single monomer in a one-pot synthesis

8.3.3 Stereochemistry of Metallocene-Catalyzed Polymerization SCHEME 8.5. A mechanism for isotactic placement with a metallocene catalyst. Optically active isotactic polymer would form from a pure enantiomer of 8

8.4 Ziegler-Natta Copolymerization
(R:aliphatic) CnH2n+1 n=2일 경우 LLDPE n=1일 경우 EPDM(EPM) TABLE 8.5 ethylene is much more reactive than higher alkenes with both heterogeneous and homogeneous catalysts. EPDM is prepared with small amounts of a nonconjugated diene to facilitate crosslinking. 13 14 15 Typical dienes ethylidenenorborene dicyclopentadiene 1,4-hexadiene

a Data from Boor3 and Kamisky.22
TABLE Representative Reactivity Ratios in Ziegler-Natta Copolymerizationa Monomer 1 Monomer 2 Catalystb r1 r2 Heterogeneous Ethylene Propylene Homogeneous 1-Butene 1-Hexene TiCl3/AlR3 VCl3/AlR3 Cp2ZrMe2 [Z(Ind)2]ZrCl2c 15.72 5.61 26.90 4.04 31 6.6 55 69 0.110 0.145 0.043 0.252 0.005 0.06 0.017 0.02 a Data from Boor3 and Kamisky.22 b R = C6H13; Cp = cyclopentadiene; Me = methyl; Z = bridging group; Ind = indene. c Z = CH2CH2.

8.5 Supported Metal Oxide Catalysts
Typical supports : Alumina, silica, charcoal (숯) metals : Cr, V, Mo, Ni, Co, W, Ti etc Prepare of Catalysts ① The support material is impregnated with the metal ion, then heated in air at a high temperature to form the metal oxide. ② when the support material is an oxide such as alumina, the two oxides are coprecipitated and dried in air. Catalyst is activated treatment with a reducing agent (hydrogen, metal hydride, carbon monoxide) Poisoning of the catalyst in the presence of water, oxygen, acetylene.

8.5 Supported Metal Oxide Catalysts
(8.23) Character of the supported metal oxides ① yield polyethylene with approximately equal amounts of saturated and unsaturated chain ends. ② not as active as Ziegler-Natta catalysts, and they do not give rise to a high degree of steroregularety.

effective in polymerizing butadiene and isoprene
8.6 Alfin Catalysts alcohol + olefin effective in polymerizing butadiene and isoprene to very-high-molecular-weight polymer The most effective catalyst for diene polymerization - allylsodium, sodium isopropoxide, sodium chlofide (8.24) (8.25) (8.26) polymerize butadiene within minutes to a polymer having a molecular weight of several million

8.7 Metathesis Polymerization
Alkenes undergo a double bond redistribution reaction (8.27) (8.28) 16 17

8.7 Metathesis Polymerization
Synthesis of polymers by olefin metathesis (8.29) (8.30) acylic dienes

8.7.1 Ring-Opening Metathesis Polymerization
Propagation steps (8.31) That certain group Ⅷ metal compounds (8.32) 18 7-oxanorbornene derivatives

Examples of three metathesis polymerizations
(8.33) 19 (8.34) 20 (8.35) 21 polyoctenamer norbornene polymer

with cyclic polyenes 22 (8.36) (8.38) 24 23 1—methyl-1,5-cyclooctadiene cis,trans-cyclodeca-1,5-diene 1,3,5,7-cyclooctatetraene

8.7.2 Acyclic Diene Metathesis Polymerization
ADMET(Acyclic diene metathesis) polymerization of 1,9-decadiene (8.39) ADMET is also useful for the synthesis of functionalized polymers. the symthesis of an unsaturated polymer containing ester functionality. (8.40)

byproduct of ADMET polymerization
8.7.2 Acyclic Diene Metathesis Polymerization addition of ethylene to an unsaturated polymer can effect depolymerization byproduct of ADMET polymerization (8.41)

9.1 Introduction 9.2 Functional 9.3 Ring-forming reactions 9.4 Crosslinking 9.5 Block and graft copolymer formation 9.6 Polymer degradation

Polymeric reagents and polymer-bound catalysts
9.1 Introduction Applications of chemical modifications : Ion-exchange resins Polymeric reagents and polymer-bound catalysts Polymeric supports for chemical reactions Degradable polymers to address medical, agricultural, or environmental concerns Flame-retardant polymers Surface, treatments to improve such properties as biocompatibility or adhesion, to name a few The purpose of this chapter : To summarize and illustrate chemical modifications of vinyl polymers.

reactions that introduce cyclic units into the polymer backbone
9.1 Introduction Five general categories reactions that involve the introduction or modification of functional groups reactions that introduce cyclic units into the polymer backbone reactions leading to block and graft copolymers crosslinking reactions degradation reactions Polymer reaction시 고려사항 molecular weight crystallinity conformation, steric effect neighboring group effect polymer physical form의 변화

9.1 Introduction (9.1) neighboring group effect

9.2 Functional Group Reactions
9.2.1 Introduction of new Functional Groups Chlorination (9.2) chlorosulfonation (9.3)

9.2.1 Introduction of new Functional Groups Properties of polyethylene by chlorination ① Flammability – decrease ② Solubility – depending on the level of substitution ③ Crystalline – more (under heterogeneous conditions) ④ poly(vinyl chloride) – Tg increase Chlorosulfonation – provides sites for subsequent crosslinking reactions

9.2.1 Introduction of new Functional Groups Fluorination (9.4) Teflon - to improve solvent barrier properties. Aromatic substitution reactions (nitration, sulfonation, chlorosulfonation, etc.) occur readily on polystyrene useful for manufacturing ion-exchange resins useful for introducing sites for crosslinking or grafting

9.2.1 Introduction of new Functional Groups (9.6) introducing new functionalities (9.5) Chlorometylation Introduction of ketone groups – via the intermediate oxime

9.2.2 Conversion of Functional Groups
(9.7) Reason useful To obtain polymers difficult or impossible to prepare by direct polymerization. alcoholysis of poly(vinyl acetate) (unstable enol form of acetaldehyde)

(9.9) (9.8) Examples Saponification of isotactic or syndiotactic poly(trimethylsily methacrylate) to yield isopactic or syndiotactic poly(methacrylic acid) 2. Hofmann degradation of polyacrylamide to give poly(vinyl amine)

(9.10) Synthesis of “head-to-head poly(vinyl bromide)” by controlled brominaion of 1,4-polybutadiene

(9.11) (9.13) Other types of “classical” functional group conversions dehydrochlorinaion of poly(vinyl chloride) hydroformylation of polypentenamer hydroboration of 1,4-polyisoprene (9.12)

(9.14) Conversion of a fraction of the chloro groups of poly(vinyl chloride) to cyclopentadienyl Converting the end groups of telechelic polymers. (9.16) (9.15) Dehydrochlorination of chlorine-terminated polyisobutylene Subsequent epoxidation

9.3 Ring-Forming Reactions
Introduction of cyclic units greater rigidity higher glass transition temperatures improved thermal stability – carbon fiber (graphite fiber)

(9.17) (9.18) Ladder structures - Poly(methyl vinyl ketone) by intramolecular aldol condensation Nonladder structures - Dechlorination of poly(vinyl chloride)

(9.19) Cyclization reaction be made to approach its theoretical limits. when R = C3H7, commonly called poly(vinyl butyral) Plastic film (9.20) Commercially important cyclization - epoxidation of natural rubber

(9.21) (9.22) Rubber and other diene polymers undergo cyclization in the presence of acid cis-1,4-polyisoprene Quantitative cyclization of 1,2-polybutadiene - with metathesis catalysts

9.4 Crosskinking (9.23) (9.24) (9.25) (9.26) (9.27) (9.28)
Vulcanization (9.23) (9.24) (9.25) (9.26) (9.27) (9.28)

The oldest method of vulcanization
9.4 Crosskinking Vulcanization (9.29) (9.30) (9.31) The oldest method of vulcanization involving addition to a double bond to form an intermediate sulfonium ion then abstracts a hydride ion Termination - by reaction between sulfenyl anions and carbocations

organosulfur compounds increase
9.4 Crosskinking Vulcanization Rate of vulcanization 2 tetramethylthiuram disulfide 1 zinc salts of dithiocarbamic acids accelerator organosulfur compounds increase by the addition of accelerators or organosulfur compounds

9.4.2 Radiation Crosslinking
When vinyl polymers are subjected to radiation crosslinking and degradation Generally, both occur simultaneously Degradation predominates with high doses of radiation With low doses the polymer structure determines which will be the major reaction. Disubstituted polymers tend to undergo chain scission With monomer being a major degradation product priority of reaction

poly(-methylstyrene), poly(methyl methacrylate), polyisobutylene - decrease in molecular weight on exposure to radiation halogen-substituted polymers ~poly(vinyl chloride) - break down with loss of halogen most other vinyl polymers - crosslinking predominates A limitation of radiation crosslinking that radiation does not penetrate very far into the polymer matrix The method is primarily used with films

(9.32) R (9.34) Mechanism of crosslinking (9.33) fragmentation reactions

9.4.3 Photochemical Crosslinking (Photocrosslinking)
Applications electronic equipment printing inks coatings for optical fibers varnishes for paper and carton board finishes for vinyl flooring, wood, paper, and metal curing of dental materials Two basic methods incorporating photosensitizers into the polymer, which absorb light energy and thereby induce formation of free radicals (2) incorporating groups that undergo either photocycloaddition reactions or light-initiated polymerization

When triplet sensitizers (benzophenone) are added to polymer (1) incorporating photosensitizers into the polymer, which absorb light energy and thereby induce formation of free radicals Benzophenone UV흡수 n   (들뜬상태) radical 생성 (9.35) (9.36) -cleavage of the excited chain cleavage

(9.37) Poly(vinyl ester) : -cleavage reaction (2) incorporating groups that undergo either photocycloaddition reactions or light-initiated polymerization 2 + 2 cycloaddition cyclobutane crosslinks

9.4.3 Photochemical Crosslinking
SCHEME 9.2. Photocrosslinking (a) by 2 + 2 cycloaddition and (b) by 4 + 4 cycloaddition. (a) (b)

Type Structure continued
TABLE Group Used to Effect Photocrosslinking21-58 Type Structure Alkyne Anthracene Benzothiophene dioxide Chalcone Cinnamate Coumarin continued

Type Structure continued TABLE 9.1. (continued) Dibenz[b, f]azepine
Diphenylcyclopropenecarboxylate Episulfide Maleimide (R=H, CH3, Cl) continued

Type Structure TABLE 9.1. Stilbazole Stilbene Styrene
1,2,3-Thiadiazole Thymine

9.4.3 Photochemical Crosslinking
(9.38) 4 (9.39) Photo – reactive groups 의 도입 방법 ① 중합 반응 동안에 고분자에 도입 ② 미리 형성된 고분자에 반응기를 첨가

9.4.4 Crosslinking Through Labile Functional Groups
(9.40) (9.41) Reaction between appropriate difunctional or polyfuntional reagents with labile groups on the polymer chains - Crosslinking (9.42) (Friedel-Crafts reaction)

9.4.4 Crosslinking Through Labile Functional Groups
(9.43)  Cyclopentadiene-substituted polymer의 Diels-Alder reaction Thermoplastic Elastomers ( 열에 의해 재 가공이 가능)

9.4.5 Ionic Crosslinking The hydrolysis of chlorosulfonated polyethylene with aqueous lead oxide (9.44) 5 poly[ethylene-co-(methacrylic acid)] 상품명 : ionomer

which makes the polymer transparent.
9.4.5 Ionic Crosslinking Properties of Ionomers ① Introduction of ions causes disordering of the semicrystalline structure, which makes the polymer transparent. ② Crosslinking gives the polymer elastomeric properties, but it can still be molded at elevated temperatures. ③ Polarity , adhesion

9.4.5 Ionic Crosslinking Application of Ionomers coatings adhesive layers for bonding wood to metal blow-molded and injection-molded containers golf ball covers blister packaging material binder for aluminosilicate dental fillings

9.5 Block and Graft Copolymer Formation
9.5.1 Block Copolymers (9.45) (9.46) 1. Polymer containing functional end groups 사용 2. Peroxide groups introduced to polymer chain ends 사용 개시제의 역할

9.5.1 Block Copolymers (9.47) (9.48) 3. Peroxide units 사용

9.5.1 Block Copolymers 4. Another way to form chain-end radicals - mechanical degradation of homopolymers (using ultrasonic radiation or high-speed stirring) EX) Polyethylene-block-polystyrene

A monomer is polymerized in the presence of a polymer with branching
9.5.2 Graft Copolymers A. Three general methods of preparing graft copolymers A monomer is polymerized in the presence of a polymer with branching resulting from chain transfer. (2) A monomer is polymerized in the presence of a polymer having reactive functional groups or positions that are capable of being activated (3) Two polymers having reactive functional groups are coreacted.

polymer, monomer, and initiator
9.5.2 Graft Copolymers 1) Three components polymer, monomer, and initiator 2) The initiator may play one of two roles It polymerizes the monomer to form a polymeric radical (or ion or coordination complex), which, in reacts with the original polymer ② it reacts with the polymer to form a reactive site on the backbone which, in turn, polymerizes the monomer. (1) Chain transfer

double bonds in polydienes carbonyl groups
9.5.2 Graft Copolymers 3) Consideration 4) Grafting sites At carbons adjacent to double bonds in polydienes carbonyl groups ① reactivity ratios of monomers ② To take into account the frequency of transfer determine the number of grafts. : That are susceptible to transfer reactions

Group that undergoes radical transfer readily
9.5.2 Graft Copolymers (9.49) . At carbons adjacent to carbonyl groups EX Mixture of poly(vinyl alcohol)-graft-polyethylene and long-chain carboxylic acids 5) Grafting efficiency improvement Group that undergoes radical transfer readily (mercaptan is incorporated into the polymer backbone.

9.5.2 Graft Copolymers (9.50) 6) Cationic chain transfer grafting Styrene is polymerized with BF3 in the presence of poly(p-methoxystyrene) Friedel-Crafts attack

Synthesis of poly(p-chlorostyrene)-graft-polyacrylonitrile
9.5.2 Graft Copolymers (2) Grafting by activation by backbone functional groups (9.51) Synthesis of poly(p-chlorostyrene)-graft-polyacrylonitrile

Major difficulty settlement
9.5.2 Graft Copolymers Irradiation – provide active sites with ultraviolet or visible radiation with or without added photosensitizer with ionizing radiation Major difficulty substantial amounts of homopolymerization = grafting settlement This has been obviated to some extent by preirradiating the polymer prior to addition of the new monomer.

Polymer – very sensitive to radiation Monomer – not very sensitive
9.5.2 Graft Copolymers Direct irradiation of monomer and polymer together Best combination Polymer – very sensitive to radiation Monomer – not very sensitive ( Sensitivity measurement – G values) TAB.9.2. Irradiation grafting of polymer emulsions - effective way to minimize

Poly(vinyl chloride) and butadiene
9.5.2 Graft Copolymers TABLE 9.2. Appoximate G Values of Monomers and Polymersa Monomer G Polymer Butadiene Styrene Ethylene Acrylonitrile Methyl methacrylate Methyl acrylate Vinyl acetate Vinyl chloride Very low 0.70 4.0 6.3 10.0 Polybutadiene Polystyrene Polyethylene - Poly(methyl methacrylate) Poly(methyl acrylate) Poly(vinyl acetate) Poly(vinyl chloride) 2.0 1.5-3 6-8 6-12 10-15 aData from Chapiro.72 G values refer to number of free radicals formed per 100 eV of energy absorbed per gram of material. Good Combination Poly(vinyl chloride) and butadiene

9.5.2 Graft Copolymers (3) Using two polymers (9.52) Grafting of an oxazoline-substituted polymer with a carboxyl-terminated polymer

Limit to oxidation ( with oxygen) Breakdown of the polymer backbone
9.6 Polymer Degradation 9.6.1 Chemical Degradation Limit to oxidation ( with oxygen) Breakdown of the polymer backbone No involving pendant groups. No functional groups other than

9.6 Polymer Degradation 9.6.1 Chemical Degradation
Saturated polymers Very slowly by oxygen Autocatalytic Speed up – heat or light or by presence of certain impurities Reaction Product – numerous and include water, carbon dioxide, carbon monoxide, hydrogen, and alcohols Tertiary carbon atoms – most susceptible to attack (polyisobutylene>polyethylene>polypropylene) Crosslinking – always degradation Decomposition of initially formed hydroperoxide groups - mainly responsible for chain scission (9.53) Decomposition of initially formed hydroperoxide groups

Much more rapidly (by complex free radical )
9.6 Polymer Degradation 9.6.1 Chemical Degradation Unsaturated polymers Much more rapidly (by complex free radical ) Allylic carbon atoms – most sensitive to attack (resonance-stabilized radicals) very susceptible to attack by ozone

Three types of thermal degradation nonchain scission
random chain scission depropagation  (9.54) elimination of acid from poly(vinyl esters) ① refers to reactions involving pendant groups (9.55) elimination of alkene from poly(alkyl acrylate)s

Disadvantage of the Durham route
Thermal Degradation ② Use – approach to solving the problems of polyacetylene’s intractability 7 8 (9.56) (9.57)  tricyclic monomer precursor polymer Thermal degradation coherent films of polyacetylene Durham route Disadvantage of the Durham route : That a relatively large molecule needs to be eliminated. (9.58) Yield polyacetylene without the necessity of an elimination reaction

③ Useful of Nonchain scission reactions : Characterizing copolymers
Thermal Degradation ③ Useful of Nonchain scission reactions : Characterizing copolymers (when the amount of a volatile degradation product can be correlated with the concentration of a given repeating unit) (2) Random chain scission : Result from homolytic bond-cleavage reactions at weak points in the polymer chains (9.59)

Initiation Chain end Poly(methyl methacrylate)
Thermal Degradation Initiation Chain end Poly(methyl methacrylate) Random site along the backbone Poly(-methylstyrene) (3) Depropagation (9.60) In both case

9.6.3 Degradation by Radiation
Radiation crosslinking or degradation All vinyl polymers – tend to degrade – under very high dosages of radiation. Ultraviolet or visible light Elevated temperatures - 1,1-disubstituted polymers to degrade to monomer Room temperature – crosslinking and chain scission reactions Ionizing radiation much higher yields of monomer from 1,1-disubstituted polymers at room temperature. At comparable levels of radiation polyethylene and monosubstituted polymers – mainly crosslinking

SCHEME 9.3. Random chain scission of polyethylene.
 Degradation by Radiation

Chapter 10. Step-Reaction and Ring-Opening Polymerization
10.1 Introduction Chapter 10. Step-Reaction and Ring-Opening Polymerization 10.2 Step-reaction polymerization---Kinetics 10. 3 Stoichiometric Imbalance. 10. 4 Molecular weight Distribution 10. 5 Network Step Polymerization 10. 6 Step-Reaction Copolymerization. 10. 7 Step polymerization Techniques. 10. 8 Dendritic Polymers. 10. 9 Ring-opening polymerization. POLYMER CHEMISTRY

10.1 Introduction A. Characteristics of step-reaction polymers.
a. Polymers containing functional group in backbones b. Synthesizing dendritic polymers B. Examples of commercialized step-reaction polymers. Note) Table 10.1 POLYMER CHEMISTRY

POLYMER CHEMISTRY

10.2 Step-reaction polymerization---Kinetics
A. Types of monomer a. AB type b. AA and BB type c. Three functional group for crosslinked polymers POLYMER CHEMISTRY

10.2 Step-reaction polymerization---Kinetics
B. Condensation of difunctional monomers. a. b. POLYMER CHEMISTRY

C. Kinetics of step-polymerization.
a. Assumption : Independence on chain length. b. Rate equation and 2 Integration Combining Carothers equation. POLYMER CHEMISTRY

C. Kinetics of step-polymerization.
c. Polyesterification : self-acid catalyzed reaction. Integration Combining Carothers equation. POLYMER CHEMISTRY

10. 3 Stoichiometric Imbalance.
A. Chain length control. a. High molecular weight. b. Oligomers for free polymer. 1) Epoxy oligomer. 2) Unsaturated polyester. 3) Polyamide B. Preparing methods for oligomers. a. Quenching : unsaturated polyester. b. Stoichiometric imbalance : epoxy resin. c. Addition of monofunctional reactant. POLYMER CHEMISTRY

10. 3 Stoichiometric Imbalance.
C. Modification of Carothers equation. a. parameter r : stoichiometric imbalance. , : initial unreacted groups. , : unreacted group. if , then : Carothers equation. if , then

10. 4 Molecular weight Distribution
A. Conversion and Nx

10. 4 Molecular weight Distribution
B. Conversion and Wx C. Polydispersity index POLYMER CHEMISTRY

POLYMER CHEMISTRY

10. 5 Network Step Polymerization
A. Greater than two functionality polymers. a. Alkyd-type polyester : b. Phenol-formaldehyde resin : c. Melamine-formaldehyde resin :

B. Gelatin : High conversion of greater than two functionality. a. Gel point : onset of gelatin. sudden increase in viscosity. change from liquid to gel. bubbles no longer rising. impossible stirring. POLYMER CHEMISTRY

C. Gel point conversion. : critical reaction conversion. : average functionality. POLYMER CHEMISTRY

D. Examples of gel point conversion. 3mol of 1 2mol of 4 Gel point conversion : 77% (Experiment) 83% (Calculate) POLYMER CHEMISTRY

10. 6 Step-Reaction Copolymerization.
A. Random copolymers. 1:1:2 mixture of terephthalic acid, isophtahlic acid, ethylene glycol. B. Alternating copolymers. a. b. Randomization : Trans-esterification. POLYMER CHEMISTRY

10. 6 Step-Reaction Copolymerization.
C. Block copolymer. Telechelic polymers. a. b. c.

10. 7 Step polymerization Techniques.
A. Significant difference between vinyl and nonvinyl polymerization. a. Vinyl polymerization : Large enthalpy factor. Exotherm reaction. b. Nonvinyl polymerization : High activation energy. Low exotherm. POLYMER CHEMISTRY

B. Step polymerization techniques. a. Bulk polymerization. 1) Advantage : Free of contaminants. 2) Disadvantage : High viscosity. b. Solvent polymerization. 1) Advantage : Lower viscosity. Removing by products by azeotropic distillation. 2) Disadvantage : Solvent removing process. POLYMER CHEMISTRY

c. Interfacial polymerization. Polymerization at the interface between immiscible two solvents. Water : Diamine. Organic solvent : Diacid chloride. 1) Low temperature polymerization. 2) Rapid polymerization. 3) Higher molecular weight. 4) Not necessary stoichiometric balance. ․Schotten-Baumann reaction. POLYMER CHEMISTRY

d. Phase-transfer catalysis polymerization(PTC). 1) Phase-transfer catalyst : Benzyltriethylammonium chloride. C6H5CH2N+(C2H5)3Cl- 2) Mechanism : Dissolve in water and make ion pair. Move to organic layer.

10. 8 Dendritic Polymers. A. Terminology (Since 1980s)
Dendrimer : Dendron = like tree. Starburst polymer. B. Commercial application. a. Drug delivery system : Controlled release of agricultural chemicals b. Molecular sensors. c. Rheology modifiers. POLYMER CHEMISTRY

10. 8 Dendritic Polymers. C. Characteristics feature.
a. Structure : Three component parts. 1) Core. 2) Interior dendritic structure. 3) Exterior surface. b. Easy control macromolecular dimension by a repetitive sequence of step. c. More soluble than linear polymer : high surface functionality. d. Low viscosity : No entanglement. e. Supramolecular assembly : Guest molecules among the interior branches POLYMER CHEMISTRY

10. 8 Dendritic Polymers. D. Synthsis of dendrimer. a. Divergent :
1) Polyamidamine (PAMAM).

10. 8 Dendritic Polymers. b. Convergent.

10. 8 Dendritic Polymers. E. Hyperbranched polymer.
a. Types of monomer : AxB ( x > 1). F. Nanostructure of dendrimer. a. Molecules dimension : 1-100nm. b. Molecules devices : Mimicking nanoscopic biomolecules. POLYMER CHEMISTRY

10. 9 Ring-opening polymerization.
A. Commercially important ring-opening polymers. Ring-opening polymers : Condensation polymers. Not polycondensation reaction. No byproduct. POLYMER CHEMISTRY

POLYMER CHEMISTRY

B. Mechanism of ring-opening polymerization.
a. Initiator : Ionic or coordination species (X*). 1) 2) b. Initiator : XY. 1)

10. 9 Ring-opening polymerization.
C. Ring strain : Possibility of ring-opening polymerization. 3 > 4 > 8 > 7 > 5 > 6 D. Ring-opening block copolymerization. AB, [AB] , ABA Block copolymer. POLYMER CHEMISTRY

Polymer Chemistry Malcolm P. Stevens

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