Polymer Synthesis CHEM 421 Odian Book Chapter 5
Polymer Synthesis CHEM 421 • Odian Book Chapter 5 -2
Polymer Synthesis CHEM 421 Cationic Polymerization
Cationic Polymers Polymer Synthesis CHEM 421 Commercial and Technological Significance Chemical Name • Polyisobutylen Trade Name Formula Vistanex, Oppanol • Isobutylene-isoprene copolymer and chlorinated copolymer Butyl Rubber and Chlorobutyl ~98% ~2% Delrin • Polyoxymethylene Trioxane-epoxide copolymer Celcon ~2%
Cationic Polymers Polymer Synthesis CHEM 421 Commercial and Technological Significance Chemical Name Trade Name • Polyepichlorohydrin Hydrin Rubber Lycra or Spandex • Poly(THF) or Poly(tetramethylene oxide) • Polybischloromethyl Oxetane Penton Formula
Cationic Polymerizations Polymer Synthesis CHEM 421 R = electron releasing group R, R’= Poly(isobutylene)
Cationic Polymerization Polymer Synthesis CHEM 421 …Also cyclics Hydrin Rubber Poly(oxymethylene) Delrin
Cationic Polymerization 1) Priming 2) Initiation Step Polymer Synthesis CHEM 421
Cationic Polymerization 3) Propagation 4) CM Polymer Synthesis CHEM 421
Initiators Polymer Synthesis CHEM 421 A) Bronsted Acids ionic A can not be too nucleophilic HCl is not very good Methanesulfonic acid covalent
Initiators Polymer Synthesis CHEM 421 B) 1)Lewis Acids Sn. Cl 4, Al. Cl 3, Ti. Cl 4, BF 3 R 3 Al, R 2 Al. Cl, RAl. Cl 2 2) Co initiator
Auto Ionization Bone dry Polymer Synthesis CHEM 421
Chain Transfer Polymer Synthesis CHEM 421 More Important in Cationic than in Anionic 1) To Monomer
Chain Transfer 2) Ring Alkylation on Solvent Polymer Synthesis CHEM 421
Chain Transfer 3) Ring Alkylation on Polymer Synthesis CHEM 421
Chain Transfer Polymer Synthesis CHEM 421 4) Hydride Abstraction from Polymer
Poly(isobutylene) Low MW (Mn<50, 000 g/mol) Liquids adhesives caulking sealants motor oils - important Tpzn= 0 to – 40 o. C w/Al. Cl 3 Polymer Synthesis CHEM 421
Poly(isobutylene) High MW (Mn= 50, 000 -5, 000) Elastomeric Tpzn= – 100 o. C w/ Al. Cl 3 w/ 1 -5 % isoprene (to vulcanize) Methylchloride as solvent Slurry Polymer Synthesis CHEM 421
Butyl Rubber Advantages • Lower Temp Capability – -50 o. C NO TM – -70 o. C = TG • More Resistant to Ozone • Very Low Gas Permeability inner tire tubes Polymer Synthesis CHEM 421
Temperature Dependence _ Xn 1/T Polymer Synthesis CHEM 421
Temperature Dependence Polymer Synthesis CHEM 421 As T Termination and CT Break change in mode of CT [ions] vs [ion pairs]
Complications 3 -methyl-1 -butene As T , % isomerization Polymer Synthesis CHEM 421
Complications Polymer Synthesis CHEM 421 3 -methyl-1 -butene Temp -130 o. C -100 o. C %isomerization 100 % 70 %
Isomerization Polymer Synthesis CHEM 421
Cationic Living Polymerization Polymer Synthesis CHEM 421
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