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

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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

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

10. 5 Network Step Polymerization 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

10. 5 Network Step Polymerization C. Gel point conversion.    : critical reaction conversion.     : average functionality. POLYMER CHEMISTRY

10. 5 Network Step Polymerization 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

10. 7 Step polymerization Techniques. 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

10. 7 Step polymerization Techniques.  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

10. 7 Step polymerization Techniques.  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).

 2)

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

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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