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General Approaches to Polymer Synthesis

General Approaches to Polymer Synthesis. 1. Addition Chain Growth Polymerization of Vinyl Monomers. Ring Opening Polymerization Heterocylics Metathesis of Cyclic Olefins. 2. Condensation Step Growth   Polymerization of A-B or AA/BB Monomers. 3. Modification of Preformed Polymers

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General Approaches to Polymer Synthesis

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  1. General Approaches to Polymer Synthesis • 1.Addition Chain Growth Polymerization of Vinyl Monomers • Ring Opening Polymerization • Heterocylics • Metathesis of Cyclic Olefins • 2. Condensation Step Growth •   Polymerization of A-B or AA/BB Monomers 3. Modification of Preformed Polymers Polysaccharides Peptides and Proteins   Synthetic Precursors

  2. Major Developments in the 1950-60's Living Polymerization (Anionic) • Mw/Mn  1 • Blocks, telechelics and stars available (Controlled molecular architecture) • Statistical Stereochemical Control • Statistical Compositions and Sequences • Severe functional group restrictions

  3. Ziegler-Natta (Metal-Coordinated) Polymerization • Stereochemical Control • Polydisperse products • Statistical Compositions and Sequences • Limited set of useful monomers, i.e. olefins • SINGLE SITE CATALYSTS

  4. Additional Developments in the 1980's • "Immortal" Polymerization (Cationic) • Mw/Mn  1.05 • Blocks, telechelics, stars • (Controlled molecular architecture) • Statistical Compositions and Sequences • Severe functional group restrictions

  5. Free Radical Initiated Polymerization • Controlled Free Radical Polymerization • Broad range of monomers available • Accurate control of molecular weight • Mw/Mn  1.05 --Almost monodisperse • Blocks, telechelics, stars • (Controlled molecular architecture) • Statistical Compositions and Sequences

  6. Current Strategies in Polymer Synthesis • Objectives: Precise Macromolecular Design • 1 . Control of: Molecular Weight • Molecular Weight Distribution • Composition • Sequence of repeat units • Stereochemistry • 2.  Versatility

  7. Genetic Approaches via Modified Microorganisms • Monodisperse in MW • Monodisperse in Composition • Sequentially Uniform • Stereochemically Pure • Diverse set of functional groups possible through synthesis of novel amino acids

  8. Step-Growth or Condensation Polymerizations Molecular Weight predicted by Carothers Equation: A-A + B-B -[A-B-]x + x C [A-A] = [B-B] = No # of functional groups remaining at anytime = N Extent of reaction = p No - N p = _____ or N = No (1 - p) No Degree of Polymerization, D.P. = No / N = 1 / (1 - p)

  9. Problems in Achieving High D. P. 1. Non-equivalence of functional groups a. Monomer impurities 1. Inert impurities (adjust stoichiometry) 2. Monofunctional units terminate chain b. Loss of end groups by degradation c. Loss of end groups by side reactions with media d. Physical losses e. Non-equivalent reactivity f. Cyclization . Unfavorable Equilibrium Constant

  10. Impact of percent reaction, p, on DP Degree of Polymerization, D.P. = No / N = 1 / (1 - p) Assuming perfect stoichiometry DPmax= (1 + r) / (1 - r) where r molar ratio of reactants if r = [Diacid] / [diol] = 0.99, then DPmax= 199

  11. Cyclization 1. Thermodynamic stability Rings of: 3,4,8 < 11 < 7, 12 << 5 << 6 2. Kinetic Control Propagation more rapid than cyclization Reduce probability of collision for rings 12 Non-reversible propagation process

  12. Equilibrium in Polyesterification Reaction in closed system p = fraction esterified

  13. Equilibrium in Polyesterification Effect of Keq on extent of reaction and DP transesterification esterification amide formation

  14. Driving reaction to completion in open, driven system

  15. Types of Condensation Reactions 1. Polyesters

  16. Preparation of Aromatic Polyesters Stoichiometry and DP controlled by extent of glycol removed.

  17. Types of Condensation Reactions 2. Polyamides

  18. Polyamides via Condensation -- Nylon 66 mp. 265C, Tg 50C, MW 12-15,000 Unoriented elongation 780%

  19. Types of Condensation Polymers Polyesters Polyanhydrides Polyacetals Polycarbonates

  20. Lexan Polycarbonate Interfacial Process Tm = 270C, Tg = 145-150C 10-40 % Crystalline, Brittle Temp. - 10C Ester Interchange No Solvent, Pure Polymer with MW > 30,000 Formed

  21. Types of Condensation Polymers polyurethanes polyphenylene oxide polyarylenes polyarylene ether sulfones

  22. Low Temperature Condensation Polymerization • Interfacial or Solution in Polar Aprotic Solvents

  23. Interfacial or Solution Polymerization in Polar Aprotic Solvents (Con’t)

  24. Applications of Low Temperature Condensations • Prep. of Infusible Thermally Stable Polymers • Prep. of Thermally Unstable Polymers Prep. of Polymers Containing Functional Groups with Differing Reactivity Formation of Block or Ordered Polymers (No equilibration of polymer in melt allowed) Direct Production of Polymer Solutions for Coatings, Spinning into Fibers, Solvent Blending to form Composites

  25. Types of Condensation Polymers polyamides polyimides polybenzthiazoles polybenzoxazoles

  26. Aromatic Polyamides “Aramids” M-isomers favor formation of soluble polymers Unique solvent combination Can be Dry Spun to Fiber As Spun: Elongation, 23-34%, Tenacity, 4.6-5.3 g/Denier M.p. > 350 C 70% Strength Retained in Ionizing Radiation Nomex

  27. Polyimides for Electronic Applications Fabricate in soluble form Post treat to final form Kevlar

  28. POLYETHERSULFONES Bis-nucleophile Polymerize by SnAr2 Monofunctional terminator to stabilize polymer Use Temperature -100 to + 175C Stable in air to 500C, Self Extinguishing Molecular Weight = 65,000 - 250,000 Amorphous Material, Tg  200C, Films pressed at 280C

  29. Polyphenylene Oxide (PPO) Oxidative Coupling Process Mn 30,000 to 120,000 Amorphous , Tg  210C Crystalline, Tm  270C Brittle point  -170C Thermally Stable to  370C Noryl is a blend with polystyrene

  30. Noryl is Unique Blend • Single Phase, Tg dependent upon composition • Maximum tensile strength at 80 wt% PPO • Other properties; volume fraction weighted average • Blend compatible with rubber modified polystyrene (high impact resistance) • Applications of Noryl Engineering Thermoplastics • Useful properties • High impact resistance • Flame retardant • High chemical stability • Low moisture absorbance (0.07%0 • Use in appliance housings • Automobile dashboards • Radomes, fuse boxes, wiring splice devises

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