Silyl Radical Chemistry and Conventional Photoinitiators: A Route for the Design of Efficient Systems

Abstract

Three new efficient photoinitiators (PI) based on a well-known chromophore skeleton (hydroxyphenylacetophenone, thioxanthone, or benzoin) linked to a silyl-containing moiety are proposed. The ability of these structures to initiate both free radical polymerization and free radical promoted cationic polymerization is investigated. A comparison with parent compounds is provided. High rates of polymerization and high final conversions are obtained. These PI directly generate silyl radicals under light irradiation as characterized by ESR spin-trapping. The analysis of the excited-state processes through laser flash photolysis and quantum molecular calculations allow to explain the observed photochemical behavior. The present results evidence the high potential of these new modified PI.