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

Major Developments in the '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

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

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

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

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 –

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

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)

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 lossese. Non-equivalent reactivity f. Cyclization. Unfavorable Equilibrium Constant

Impact of percent reaction, p, on DP if p =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

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

Equilibrium in Polyesterification Reaction in closed system p = fraction esterified

Equilibrium in Polyesterification Effect of K eq on extent of reaction and DP Keq p X n , transesterification esterification amide formation

Driving reaction to completion in open, driven system KeqDP[H 2 O]

Types of Condensation Reactions 1. Polyesters

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

Types of Condensation Reactions 2. Polyamides

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

Types of Condensation Polymers Polyesters Polycarbonates Polyanhydrides Polyacetals

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

Types of Condensation Polymers polyurethanes polyphenylene oxide polyarylenes polyarylene ether sulfones

Low Temperature Condensation Polymerization Interfacial or Solution in Polar Aprotic Solvents ParameterLow TempHigh Temp Intermediates Purity Stoichiometry Heat Stability Structure Cost Moderate Not Essential Highly Reactive High Essential Thermally stable Moderate

Interfacial or Solution Polymerization in Polar Aprotic Solvents (Con’t) ConditionsLow TempHigh Temp Time Temperature Pressure Yield By-products Solvents Minutes to hours 0 – 150  C Atmospheric Low to moderate Salts Required Hours to days >250  C High to vacuum Quantitative Volatiles None

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

Types of Condensation Polymers polyamides polyimides polybenzoxazoles polybenzthiazoles

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

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

POLYETHERSULFONES Molecular Weight = 65, ,000 Amorphous Material, Tg  200  C, Films pressed at 280  C Use Temperature  to  C Stable in air to 500  C, Self Extinguishing Bis-nucleophile Polymerize by Sn Ar 2 Monofunctional terminator to stabilize polymer

Polyphenylene Oxide (PPO) Noryl is a blend with polystyrene 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 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