Phenothiazine photosensitizers for onium salt photoinitiated cationic polymerization

Phenothiazine compounds bearing a wide range of different substituents are excellent photosensitizers for onium salt cationic photoinitiators. These p hotosensitizers are generally operative in the mid- and long-range regions of the UV spectrum and are especially useful for enhancing the rate of phot oinitiated cationic polymerization carried out utilizing both filtered and broadband UV emission sources. In this article, the syntheses of several di fferent substituted phenothiazines are described and the ability of these c ompounds to photosensitize the photolysis of different onium salt photoinit iators is evaluated. Attempts were made to correlate the structure and spec tral characteristics of the phenothiazines with their efficiency of photose nsitization in the cationic photopolymerizations of several typical epoxide and vinyl ether monomers. (C) 2001 John Wiley & Sons, Inc.