1.1 Basic Polymer Chemistry 1.2 Polymer Nomenclature Polymers are the largest class of soft materials: over Polymer = 100 billion pounds of polymers made in US each year Monomer = Classification systems Polymer = Typical physical state? Mechanisms of chain growth Oligomer = Typical physical state? Polymerization = 1.3 Polymer Synthesis 1.4 Chain Growth Polymerization Two synthetic methods Addition polymerization Chain growth/addition polymerization One molecule adds to another with no net loss of atoms (high atom economy) Individual steps are typically rapid (msec, sec) Discrete steps Step growth polymerization Propagation rate >> termination rate What happens if the reaction runs longer? Do the chains get longer? Do you just get more chains? 1 1.5 Chain Growth Polymerization 1.6 Monomers for Chain Growth Addition polymerization Polymers form by… What’s in the polymerization mixture? Defining features Useful monomers for chain growth CH3 Cl CH2 CH CH CH Monomer Polymer H2C H2C H2C H2C ethylenepropylene styrene vinyl chloride nCH2 CH (CH2 CH)n X X O N X X C O O-CH3 CH2 O CH3 C HC C nCH2 CH (CH2 CH O)n CH C CH CH CH O H2C H2C 3 H2C H2C vinyl acetate methyl methacrylate butadiene acrylonitrile 1.7 Chain Growth Polymerization 2.1 Radical Polymerization Mechanisms to link monomers together Three steps to radical polymerization Radical Initiation Cationic (1) RO OR 2RO Anionic Transition metal catalysis (2) RO + H2C CH RO CH2 CH R R Propagation RO CH2 CH + H2C CH RO CH2 CH CH2 CH R R R R Termination 2 2.2 Radical Polymerization 2.3 Radical Polymerization Initiation Propagation Termination Radical Coupling polystyrene RO CH RO CH CH RO CH CH H2C CH2 H2C CH2 CH2 styrene Head attacks the tail of the next monomer What defines the “head”? Why would RO• attack the tail preferentially? Disproportionation (H abstraction) Initiation Propagation Cl Cl Cl Cl Cl RO CH RO CH CH RO CH CH polyvinylchloride H2C CH2 H2C CH2 CH2 vinyl chloride Propagation continues until … 2.4 Radical Polymerization 2.5 Radical Polymerization Chain transfer Another “termination” mechanism “back-biting” CH CH2 2 C H CH CH 4 9 CH CH2 2 CH2 CH2 CH CH2 CH2 H CH2 CH2 CH2 CH3 This is a prominent type of branch. Why would this be so? 3 2.6 Radical Polymerization 2.7 Radical Polymerization Another termination process (chloroalkanes) Monomers for radical polymerization RO (CH CH) CH CH Cl RO (CH2 CH)n CH2 CH + CCl4 2 n 2 F Cl Cl R R R R CH C + CCl3 2 F C CH F Cl H2C C H2C H2C CCl3 + CH2 CH Cl3CCH2 CH R R ethylene F 1,1-dichloroethylene vinylchloride 1,1,2,2-tetrafluoroethylene N CH2 O OCH3 HC C C C CH CH CH CH3 H C H2C H2C 2 H2C acrylonitrile 1,3-butadiene styrene methylmethacrylate 2.8 Radical Diene Polymerization 2.9 Radical Polymerization Reaction: Accounts for about ½ of all commercial polymerization nCH CH CH CH (CH CH CH CH ) 2 2 2 2 n What polymer structure forms when propylene is 1,3-butadiene polybutadiene subjected to a radical process? Mechanism: (1) ROOR 2RO (2) RO + CH2 CH CH CH2 RO CH2 CH CH CH2 Ethylene forms high molecular weight polymer but only under extreme conditions – why? (3) RO CH2 CH CH CH2 +CH2 CH CH CH2 RO CH2 CH CH CH2 CH2 CH CH CH2 Product is highly branched (where do the branches then (3), (3), (3), etc. come from?) Is it possible to make linear PE? 4 3.1 Cationic Polymerization 3.2 Anionic Polymerization Initiating and propagating species are cations Initiator and propagating species are anions Monomer attributes? Cationic polymerization of isobutene (2-methylpropene) Initiation Propagation Initiation Propagation CH3 CH3 CH3 H CH polystyrene C CH3 H C CH3 C 3 R CH R CH CH R CH CH H2C CH2 H2C CH CH Chain H2C 2 H2C 2 CH2 styrene isobutene or isobutylene titibtermination by loss of H+ CN CN CN CN CN Propagation What forms? R R CH R CH CH CH CH polyacrylonitrile CH3 CH3 H C H3C CH3 H2C CH2 2 CH2 CH2 polyisobutylene H C C CH3 C CH3 acrylonitrile H C CH2 CH2 2 3.3 Anionic Polymerization 3.4 Living Polymerization Monomer attributes? What’s a “living polymer”? Other example of monomers? Chain termination H O R CH CH CH 2 R CH CH CH + OH H CH2 CH2 n CH2 CH2 CH2 n CH2 polystyrene 5 4.1 Copolymers 4.2 Copolymers Random copolymers ABS = acrylonitrile-butadiene-styrene terpolymer CH2 CH + CH2 CH CH CH2 +CH2 CH CN SBR (styrene-butadiene rubber) CH2 CH CH2 CH CH CH2 CH2 CH nCH2 CH CN + > nCH2 CH CH CH2 Control the amount of each monomer that ends up CH CH CH CH CH CH CH CH CH CH 2 2 2 2 2 in the polymer? 4.3 Copolymers 4.4 Block Copolymers Block copolymers Polystyrene MhiMechanism an d process Polybutadiene Polybutadiene framework held together (cross-linked) by clusters of polystyrene Styrene-butadiene block copolymer SSSSSBBBSSSSSBB 6 4.5 Copolymers 5.1 Metal Catalyzed Polymerization Graft copolymers Coordination and Insertion M = Cr, Ti, Zr, Hf, V, Fe, Co, Ni, Pd, Cu Styrene-butadiene graft copolymer H2C Styrene polymerization off polybutadiene backbone CH2 L L L CH2CH3 CH2CH3 CH2 CH CH CH CH2 CH CH CH CH2 CH CH CH2 CH2CH3 M M M CH CH CH2 CH 2 2 C 2 CH2 C L L L H2 CH CH H2 H2C CH2 CH2 CH CH Could you graft polybutadiene off a polystyrene backbone? 5.2 Ziegler-Natta Catalysis 5.3 Ziegler-Natta Catalysis Chain Growth – Polyethylene (Polyethene) Chain Growth – Polypropylene (Polypropene) H2C H2C Cl Cl CH2 Cl CH3 CH2CH3 CH2CH3 Cl Cl C CH2CH3 Cl H CH2CH3 CH2CH3 Ti Ti Ti CH2CH3 CH2 CH Ti Ti Ti C 2 CH CH2 C H CH Cl Cl Cl H2 C H2 C C CH3 H C Cl Cl Cl H2 2 CH3 H2 CH3 H2C H C H2 2 CH2CH3 H H2C CH2CH3 C H C 2 Cl C 2 C H C C H Cl Cl CH 2 CH 2 CH CH Cl 3 H2 2 CH CH C 2 3 CH Ti Ti CH 3 H Ti 3 Ti CH2CH3 CH2 CH2 C Cl CH2 H2C CH Cl H2 Cl Cl H2C HC CH3 CH3 7 5.4 Ziegler-Natta Catalysis 5.5 Metal Complex Catalysis Chain Termination with Hydrogen For polypropylene, the metal center can direct the H C H C 2 Polymer chain growth – MACROGALLERIA H2 2 Polymer C C C H C Cl 2 C H2 C H2 Cl If one orientation is preferred …. then one polymer H2 H2 Ti H Ti stttructure is pre ferre d(d (ittiisotactic) H Cl H H Cl HCH3 HCH3 H CH3 H CH3 H CH3 isotactic: C C C C C H CH2 CH2 CH2 CH2 CH2 CH2 Cl CH2CH2 H Ti CH H2C Polymer CH3 HCH3 H H CH3 3 HCHH 3 H2C Cl C atactic: C C C C C C H2 H2 CH2 CH2 CH2 CH2 CH2 CH2 H2C H2 CH H CH CH3 H H CH CH3 H Cl C Cl CH2 3 H 3 3 CH2 syndiotactic: C C C C C Ti Ti CH CH CH CH H H CH2 CH2 2 2 2 2 Cl Cl 5.6 Polyethylene (PE) Types 5.7 Ziegler-Natta Catalysis Density (g/cc) Used to make a variety of polymers HDPE 0.94 - 0.97 HDPE = high density polyethylene High Density PE Formed by… Properties LLDPE 0.915 - 0.94 Linear Low Density PE H CH 2 CH2CH3 H2C LDPE 0.90 - 0.93 CH2 CH2 n Low Density PE 8 5.8 Ziegler-Natta Catalysis 5.9 Ziegler-Natta Catalysis LLDPE = linear low density polyethylene LLDPE = linear low density polyethylene mechanism H2C How are branches introduced? CHR Cl Cl Cl CH2CH3 CH2CH3 How is the branch length changed? CH2CH3 Ti Ti Ti CH2 CH C 2 Cl Cl C Cl H2 H2 How are the number and location of branches CH2 controlled? H2C H2 H2C CH2CH3 C H C H Cl C 2 CH H Cl CH2 CH2 CH2CH3 2 CHR CH2CH3 H2C Ti R Ti CH2 CH CH2 CH C 2 n Cl Cl H2 R CH2 H2C 5.10 ROMP Catalysis 6.1 Step Growth Polymerization Often referred to as condensation polymerization Metathesis L L L L M CHR L M CHR CHR No free radical or ions are necessary L M + Reactive functional groups H C CHR H2C CHR CHR 2 CH2 Ring Opening Metathesis Polymerization Polymer grows in multiple directions L L L 1:1 stoichiometry of functional groups L M CH2 L M CH2 L M A—A + B—B A—A-B—B-A—A-B—B New bonds formed during L L L step growth polymerization L M L M L M 9 6.2 Step Growth Polymerization 6.3 Step Growth Polymerization Often referred to as condensation polymerization Polymerization mixture contains wide distribution of Atom efficient? slowly growing oligomers O O H H -H O n HO C (CH ) C OH +Nn (CH ) N 2 2 4 2 6 Polyamide H H adipic acid hexamethylenediamine (HMDA) diacid + diamine O O O C (CH ) C NH (CH ) NH 2 4 2 6 n C nylon 6,6 Reactions between functional groups N H O O Amide (acid and amine) O -H2O n HO C C OH + n HO CH2 CH2 OH Ester (acid and alcohol) C Polyester O Carbonate (alcohol and acid dichloride) terephthalic acid ethylene glycol diacid + dialcohol Urethane (alcohol and isocyanate) O O O C C OCH2 CH2 O O C n O N C H O O poly(ethylene terephthalate) 6.4 Polyamides 6.5 Nylon Nomenclature First synthetic polyamide was Double-numbered: 6,6 or 6,10 poly(hexamethyleneadipamide), now called nylon 6,6 First number = Reactants? Second number = Mechanism? Single-numbered: 4 or 6 or 12 O O H H -H O Number = n HO C (CH ) C OH +Nn (CH ) N 2 2 4 2 6 H H adipic acid (C6) hexamethylenediamine (C6) O O C (CH ) C NH (CH ) NH 2 4 2 6 n nylon 6,6 molecular weight = 10,000-25,000 n = 40-110 10 6.6 Two Routes to Polyesters 6.7 Esterification Mechanism Polyester mechanism O O O O O OH + -H2O H n HO C C OH + n HO CH2 CH2 OH HO C C OH HO C C + HO CH2 CH2 OH high OH terephthalic acid ethylene glycol O O O OH H O OH -H2O C C OCH2 CH2 O HO C C OCH2 CH2 OH HO C C OCH2 CH2 OH n OH OH2 O OH O O -H+ O O HO C C O CH2 CH2 OH HO C C O CH2 CH2 OH -2n CH3OH n CH3OC C OCH3 + 2n HO CH2 CH2 OH low LeChatlier’s Principle dimethyl terephthalate (DMT) O O C C OCH2 CH2 O n 6.8 Dendrimer 6.9 Polycarbonates Polycarbonates are strong, clear plastics Carbonate = diester of carbonic acid Optical market (DVD, CD’s) CH3 O -HCl n HO C OH + n Cl C Cl CH3 phosgene dialcohol + bisphenol A dichloride CH3 O (O C OC)n CH3 11 7.1 Thermoset Polymers 7.2 Thermoset Polymers Linear polymers are typically thermoplastic Thermoset polymers are cross-linked