Synthesis and characterization of second-generation S,S-dialkyl-S-(dimethylhydroxyphenyl)sulfonium salt photoinitiators

A new, simplified method has been developed for the synthesis of S,S-dialkyl-S-(dimethylhydroxyphenyl)sulfonium salt cationic photoinitiators. This novel method has successfully been used for the preparation of S,S-dialkyl-S-(3,5-dimethyl-4-hydroxyphenyl)sulfonium and S,S-dialkyl-S-(3,5-dimethyl-2-hydroxyphenyl)sulfonium salts showing a wide variation in the length and structure of the alkyl chains on the positively charged sulfur atom. These photoinitiators can also be prepared with a wide variety of different anions. The manipulation of the lengths of the alkyl chains permits the design of compatible photoinitiators for highly nonpolar monomers and oligomers such as epoxy-functional silicones, epoxidized polybutadiene, and epoxidized vegetable oils. This article describes the synthesis and characterization of these photoinitiators. (C) 2003 Wiley Periodicals, Inc.