A glance at violet LED sensitive photoinitiators based on the spiroxanthene scaffold

Abstract

A novel photoinitiator based on a spiroxanthene scaffold in the presence of an iodonium salt is proposed for the cationic ring-opening polymerization of a diepoxide, as well as for the free-radical polymerization of an acrylate upon violet LED exposure (385 and 405 nm). Good-to-excellent rates of polymerization and final conversions are obtained. These systems are characterized by a higher reactivity compared with that of anthracene/iodonium salt used as reference for cationic near UV polymerization. The addition of a poly(ionic liquid) improves the cationic polymerization profiles. The photochemical mechanisms are studied by steady-state photolysis, fluorescence, and electron spin resonance spin-trapping techniques. Molecular orbital calculations give an insight into the light absorption properties.