General Approaches to Polymer Synthesis 1 Addition

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

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

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 1. 05 --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 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 losses e. Non-equivalent reactivity f. Cyclization . Unfavorable Equilibrium Constant

Impact of percent reaction, p, on DP Degree of Polymerization, D. P. = No / N = 1 / (1 - p) Assuming perfect stoichiometry if p = 0. 5 0. 7 0. 9 DP = 2 3. 3 10 0. 95 0. 999 20 1000 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 Keq on extent of reaction and DP Keq esterification amide formation Xn 0. 01 transesterification p 0. 1 1. 11 1 0. 5 2 16 0. 8 5 81 0. 9 10 361 0. 95 20 9800 0. 99 100 39, 600 0. 995 200

Driving reaction to completion in open, driven system Keq 1 16 DP 2 20 50 [H 2 O] 2. 5 0. 0132 0. 00204 100 200 5 20 50 100 200 0. 000505 0. 000126 4. 0 0. 211 0. 0327 0. 0081 0. 00201

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. 265 C, Tg 50 C, MW 12 -15, 000 Unoriented elongation 780%

Types of Condensation Polymers Polyesters Polycarbonates Polyanhydrides Polyacetals

Lexan Polycarbonate Interfacial Process Tm = 270 C, Tg = 145 -150 C 10 -40 % Crystalline, Brittle Temp. - 10 C 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 Parameter Intermediates Purity Stoichiometry Heat Stability Structure Cost Low Temp High Temp Moderate Not Essential Highly Reactive High Essential Thermally stable Moderate

Interfacial or Solution Polymerization in Polar Aprotic Solvents (Con’t) Conditions Low Temp High 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 polybenzoxazoles polyimides polybenzthiazoles

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 Nomex M. p. > 350 C 70% Strength Retained in Ionizing Radiation

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

POLYETHERSULFONES Bis-nucleophile Polymerize by Sn. Ar 2 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

Polyphenylene Oxide (PPO) Oxidative Coupling Process Noryl is a blend with polystyrene 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