PHOTOINITIATED CATIONIC RING-OPENING POLYMERIZATION OF A CYCLOSILOXANE

Hexamethylcyclotrisiloxane was found to undergo photoinitiated cationi c ring-opening polymerization in solution and bulk, upon exposure to U V radiation, in the presence of either sulfonium or iodonium salts or an iminosulfonate derivative. Glass transition temperatures were below -100 degrees C. Molecular weights, determined by size exclusion chrom atography relative to polystyrene standards, increased with photolysis lamp intensity. Use of an iodonium photoinitiator afforded poly(dimet hylsiloxane) with Mn = 172,000. Polymerization of hexamethylcyclotrisi loxane was accompanied by a small increase in volume (3-4%).