Polymer Synthesis CHEM 421 Methods for Polyester Synthesis Direct reaction Acid halide / hydroxyl Transesterification Melt acidolysis

Polymer Synthesis CHEM 421 Direct Reaction Self-catalyzed R p [OH] [COOH] [COOH] Catalyzed by added acid ( [H + ] = constant) R p [OH] [COOH] Faster Dacron TM, Mylar TM

Polymer Synthesis CHEM 421 Terephthalic Acid Synthesis Early catalysts not quantitative…

Polymer Synthesis CHEM 421 Transesterification

Polymer Synthesis CHEM 421 Transesterification

Polymer Synthesis CHEM 421 Transesterification Diol T g ( o C) T m ( o C) 80265

Polymer Synthesis CHEM 421 Continuous Process

Polymer Synthesis CHEM 421 Primary Degradation Pathway

Polymer Synthesis CHEM 421 Primary Degradation Pathway Acetaldehyde < 3 ppm for taste Anhydride intermediate Hydrolytically unstable

Polymer Synthesis CHEM 421 Chip X-tallizes T g < T < T m Solid State PolymerizationSPP 12h Residence Time 12h Residence Time Increased MW Increased MW Minimizes Acetaldehyde Minimizes Acetaldehyde EG N2N2N2N20.9

Polymer Synthesis CHEM 421 PET Recycling 1997 – 13 million tons; 1.5 million tons for bottles1997 – 13 million tons; 1.5 million tons for bottles Ind. Eng. Chem. Res., Vol. 36, No. 4, 1997 Methanolysis; catalyst – usually Zn(OAc) 2Methanolysis; catalyst – usually Zn(OAc) 2 Copolymers pose problems – no well-definedCopolymers pose problems – no well-defined decomposition Ex. branching decomposition Ex. branching

Polymer Synthesis CHEM 421 Acid Chlorides More reactive than acidMore reactive than acid Use w/ less reactive diolsUse w/ less reactive diols Solution or interfaciallySolution or interfacially Drawbacks?Drawbacks?

Polymer Synthesis CHEM 421 Melt Acidolysis Melt Polym’z Acetic Acid 250 °C Vac Avoids side rxnsAvoids side rxns High tempsHigh temps HeterogeneousHeterogeneous LCP’sLCP’s

Polymer Synthesis CHEM 421 Polyamides Two major classes –Fibers –Engineering resins Nylon –Invented in 1930s…stockings! –1940s (WWII) all production went to parachutes, airplane tire chords, glider tow rope, military apparel –Today »Apparel »Carpet »Automotive »Security (Kevlar,Nomex)

Polymer Synthesis CHEM 421 Polyamides Nylon 6, 6 # carbons in diamine # carbons in diacid

Polymer Synthesis CHEM 421 Nylon 6,6: Nice balance of properties –Tm = 265 C –50% crystalline (high) (solvent resistant) –Easily oriented (fibers) –High strength –Abrasion resistant –Dyeable –Resistant to alkaline solution Problem –Moisture pick-up –Not resistant to acid hydrolysis

Polymer Synthesis CHEM 421 Polyamides: Structure / Property Relationships XYNameTm 46Nylon 4,8278 C 47Nylon 4,9233 C 49Nylon 4,11223 C 64Nylon 6, 6265 C 66Nylon 6, 8250 C 69Nylon 6, C

Polymer Synthesis CHEM 421 Synthesis of Polyamides Direct amidation (“Nylon Salt”) Acid chlorides / Amines Phosphorylations (Ring opening)

Polymer Synthesis CHEM 421 Direct “Nylon Salt” Route ppt’d salt T m = 183 C

Polymer Synthesis CHEM 421 Acid Chloride / Amine Route Acid chlorides more reactive Expensive Less nucleophilic aromatic amines Interfacial route –Fast –Does not require 1:1 stoichiometry –Rp is f(surface area) Solution route

Polymer Synthesis CHEM 421 Solution Acid Chloride Route

Polymer Synthesis CHEM 421 Phophorylation Route Motivation: Use cheaper diacid route instead of expensive diacid chloride route with less nucleophilic aromatic amines