Cationic Photoinitiators: Photochemistry of Triarylsulfonium: Salts In Polymer Films

1. Introduction

Triarylsulfonium salts have found prominence in the electronics industry for photoinitiated
acid catalyzed reactions of polymers and oligomers. There have also been uses for
sulfonium salts in polymer films for photo-doping and photo-optical applications. This
wide range of uses for triarylsulfonium salts has prompted interest into mechanistic studies
of the photodecomposition pathways in both solution and polymeric 8-10 Early
studies proposed that the singlet excited state of the sulfonium salt cleaved by homolysis
of the C-S bond. Later studies however presented evidence for heterolysis of the
C-S bond. In the last few years the importance in-cage recombination - cage-escape
reactivity of triarylsulfonium salts was discovered. In this paper we will describe some
of the recent new reactions of triarysulfonium salts in solution and polymer films. Also the mechanisms for sensitization of sulfonium slats in solution and for polymerization reactions will be discussed.