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Anionic Synthesis of Liquid Polydienes and Their Applications

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Presentation on theme: "Anionic Synthesis of Liquid Polydienes and Their Applications"— Presentation transcript:

1 Anionic Synthesis of Liquid Polydienes and Their Applications
Taejun Yoo* and Steven Henning October 14, 2009

2 Contents Anionic synthesis of liquid polydienes
Microstructure Macrostructure Functionalization Structure and properties Applications

3 Additives for rubber products
Liquid polydiene Low molecular weight homopolymers or copolymers containing unsaturated carbon-carbon double bonds Curing by sulfur or peroxides Liquid polydiene Elastomer Molecular weight 1,000-10,000 100,000-1,000,000 Physical state Viscous liquid Solid Processing Low shear High shear Polymerization type Batch or semi batch Batch or continuous Modification Easy Relatively harder Catalyst cost on product Critical Negligible Application Additives for rubber products Main rubber products

4 Why anionic polymerization? A variety of different liquid polymers !
Microstructure Polymer composition (styrene, butadiene, isoprene) Mode of addition (1,4- and 1,2- vinyl or 3,4-vinyl) Monomer sequence distribution (random, tapered or block) Cyclic structure (batch vs. semi batch) Macrostructure Molecular weight and distribution Molecular geometry (linear and branched) Functionalization In chain Chain end: mono and difunctional (telechelic) A variety of different liquid polymers !

5 Commercial liquid polydienes (anionic)
Plastikator 32 Butarez (HTPB and CTPB) Producer Liquid polymer Trade name MW 1,2-vinyl (%) Functional group Post polymerization Modification Nippon Soda PB Nisso 1k-4k 85-90 OH, COOH Maleinization Hydrogenation Sartomer PB, SBR Ricon Krasol 1.5k-8k 2k-10k 20-90 60-65 OH Epoxidation Synthomer Lithene 1k-9k 10-55 Kuraray PB, PI SBR, SIR LBR LIR 25-50k -

6 Microstructure Mode of addition (1,4- vs. 1,2-) Cyclic vinyl formation
Reaction conditions Comonomer effect in copolymerization Cyclic vinyl formation

7 Microstructure of polydienes
Tg (°C) Tm (°C) Cis 1,4- - 107 2 Trans 1,4- -106 97/145 Isotactic 1,2 -15 128 Syndiotactic 1,2 -28 156 1,2-vinyl* -4 - * amorphous

8 Counter ion and initiator concentration effect
Lithium catalyst soluble in hydrocarbon solvents the lowest 1,2-vinyl content good low temperature properties Catalyst Cis-1,4 Trans-1,4 1,2 Lithium 35 52 13 Sodium 10 25 65 Potassium 15 40 45 Rubidium 7 31 62 Cesium 6 59 Initiator Concentration (M) 1.4-Cis (%) 1,4-Trans (%) 3,4-Vinyl (%)* PI 6.12x10-2 74 18 8 1.0x10-3 78 17 5 1.0x10-4 84 11 0.8x10-5 97 3 PB 5x10-1 53 47 5x10-2 90 10 5x10-3 93 7 * 1,2-vinyl for polybutadiene

9 Polar additive and Temperature effect
Free ions aggregated Contact ion pair Polar solvent Presence of Lewis base (alkali metal alkoxides) in HC solvent Monodendate vs. Bidendate Temperature T.A. Antkowiak, A.E. Oberster, A.F. Halasa, and D.P. Tate JPS, Part A-1 Vol. 10, 1319 (1972) Polybutadiene with the highest 1,2-vinyl can be prepared in polar solvent at lower reaction temperature

10 Comonomer effect (random copolymerization)
Adding polar additives Maintaining the concentration of comonomer with a lower monomer reactivity ratio high during the copolymerization. Effect of styrene content on 1,2-vinyl formation in styrene-butadiene copolymerization The presence of styrene in copolymerization results in less 1,2-vinyl content than BD homopolymerization due to steric effect between allylic chain end and styrene unit.

11 Cyclization of polybutadiene
High 1,2-vinyl Lewis base Reaction temperature Monomer starving condition Batch vs. Continuous Monomer feed rate G. Quack and L. J. Fetters, Macromolecules, 11, 369 (1978). Cyclization is favorable in monomer starved reaction condition Cyclization consumes 1,2-vinyl

12 Cyclization of polybutadiene (continuous system)
Cyclization reaction increases as polar additive amount increases (higher 1,2-vinyl) reaction temperature increases (Ea cyclization>Ea propagation)

13 Cyclization of polybutadiene
Total 1,2-vinyl Cyclic vinyl 76 18 26 77 29 Stiff structure increases Tg Logh ~ (T-Tg)-1 Cyclic vinyl has more impact on the physical properties than 1,2-vinyl

14 Macrostructure Molecular weight (gram of monomer/moles of initiator)
Molecular weight distribution (Ki >Kp, Xw/Xn=1+1/Xn) Branched structure (linking reaction and transmetallation)

15 Chain transfer reaction
Ea chain transfer > Ea propagation thermodynamic control kinetic control Not applicable for functionalized polymer Cost reduction of liquid polymer production

16 Chain transfer reaction
Mn calculated: 6,830 Mn measured : 6,120 PI: 1.57 Mn calculated: 17,750 Mn measured : 1,830 PI: 3.54 Chain transfer reaction in lithium initiated anionic polymerization increases as size of counter ion increases (Li < Na <K ) polar additive amount increases (Li) reaction temperature increases (Ea chain transfer >Ea propagation) monomer feed rate decreases and chain transfer reaction is maximized in pure toluene

17 Branched polymer [h]b < [h]l
# of branch Length of branch MW of backbone Type of branch (star, graft and hyper branched) Reduction in melt and solution viscosities Processing benefits, applications

18 Branched polymers by linking reactions
Chlorosilane SiCl4 + 4 PLi SiP4 + 4LiCl Divinylbenzene DVB core * * * = reactive chain end + Epoxy and silanol compounds PLi + P-OH OH OH OH OH OH OH OH Quirk and Zhou US patent 7,235,615

19 Functionalization Chain end functionalization
Post polymerization modification (Functional groups are randomly distributed on polymer backbone)

20 Chain end functionalization
Functional agent Protected functional initiator or agent a- or w-functionalized polymer by deprotection Difunctional initiator (HTPB) (CTPB)

21 Post polymerization modification
Hydrogenation (thermal stability and copolymer) Epoxidation Maleinization 1,2 > 1,4 1,4 > 1,2 1,4 > 1,2 Esterification Addition of acryl group Imidization

22 Structure-Property Relationships

23 Molecular weight effect
Properties that depend on chain ends Properties that depend on entanglement Entanglement Intermolecular interaction Number of end groups Mw Mn Melt viscosity h=KMwa Izod impact resistance Tensile strength Flexural modulus Tg and Tm

24 J. T. Gruver and G. Kraus, J. Polym. Sci. Part A, 2, 797 (1964)
Viscosity Macrostructural (MW) effect Mcr h0=KMwP P=1 P=3.4 Newtonian Region Low MW High MW Log shear rate () Log ha 1 2 3 . Broad MWD Shear thinning J. T. Gruver and G. Kraus, J. Polym. Sci. Part A, 2, 797 (1964) Random coils Oriented coils Mcr Polybutadiene: 6,000 Polyisoprene: 10,000

25 Viscosity Microstructural effect
Zero shear viscosity data (Brookfield) as a function of both molecular weight and microstructure using a series of commercially available liquid polydiene grades ( low vinyl polybutadiene,  high vinyl polybutadiene,  poly(butadiene-co-styrene). Viscosity of liquid polydiene is dependant on MW as well as microstructure: high vinyl polybutadienes > SBR copolymers > low vinyl polybutadienes

26 Viscosity Functional group effect on chain end functionalized PB

27 Glass transition temperature
Tg = Tg() - (A/Mn) Tg as a function of vinyl content and molecular weight for a series of commercially available liquid polybutadienes. Tg as a function of comonomer content for a series of butadiene-isoprene copolymers.

28 Glass transition temperature
Functional group effect Tg as a function of oxiran content for a series epoxidized liquid polybutadienes.

29 Molecular weight dependency of crosslinking rate of polyisoprene
Microstructure (1,2- vs. 1,4) Macrostructure Sulfur crosslinking Molecular weight dependency of crosslinking rate of polyisoprene Mc of diene elastomers: ~ 12,000 g/mol Liquid polydienes do not form elastically effective crosslinks Mizuho Maeda, RubberChem 2006

30 Applications Functional additives Low viscosity (processing)
Similar chemical properties of elastomers (vulcanization) Outstanding properties (High thermal stability, good moisture and chemical resistance, good adhesive characteristics and excellent electrical properties)

31 Unfunctionalized liquid polydienes
Processing aids Low viscosity, non-toxic, low volatility and no bleeding (miscible with rubbers and non- extractable) Coagents 1,2-polybutadiene for peroxide cure of elastomers Wire and cable applications (better heat aging, fluid resistance and electrical properties) Engineering rubber products (belts, hoses, gaskets and rollers) Coating and potting agents Autoxidation with baking or metallic driers (high level of unsaturation) Tire application HVPB and SBR: wet traction LVPB: wear, low temperature properties

32 Functionalized liquid polydienes
Propellant binder: HTPB and CTPB Adhesion promoters: Maleinized PB Polyurethanes: HTPB Epoxy resin modification: HTPB and CTPB UV curing: Deoxidized, acrylated PB Nanocomposite Polymer-filler interaction

33 Summary The microstructure and macrostructure affect the Tg and bulk viscosity of final diene resin products. Lithium-based anionic polymerization provides liquid polydienes with a variety of microstructure and macrostructure including functionalization. The unique characteristics of liquid polydiene products has led to their utility in a wide variety of markets and applications such as functional additives for rubber and other thermosets, modification of thermoplastics, adhesives, and coatings.


35 Adhesion Potential - Metal
5 phr coagent LVPB-MA HVPB-MA EPDM, Peroxide cure PB-MA adhesion promoters increase adhesive bond strength

36 Thermoplastic polyurethanes
HTPB / Diisocyanate / Diol chain extender PU hard domains elastomeric soft segment Melt Flow T < Tsoftening T > Tsoftening Vulcanizate Adhering a Urethane component to a Rubber Compound substrate Diene-segments interpenetrate and co-cure with rubber compound Urethane segments bond to similar structure in PU Functional Additive to a traditional Rubber Compound varied loading increases impact on physical properties impart modulus while minimizing hysteresis (vs. TPE) realize advantages from phase structure at higher loading

37 Intercalated nanocomposite Exfoliated nanocomposite
Polymer Layered clay + Intercalated nanocomposite Exfoliated nanocomposite An organophilic clay can be produced from a normally hydrophilic clay by ion exchange with an organic cation such as an alkylammonium ion. For example, in montmorillonite, the sodium ions in the clay can be exchanged for an amino acid such as 12-aminododecanoic acid (ADA): Na+-CLAY + HO2C-R-NH3+Cl- .HO2C-R-NH3+-CLAY + NaCl Mechanical and thermal properties Permeability Flame retardance UV resistance

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