D-π-A-type aryl dialkylsulfonium salts as one-component versatile photoinitiators under UV/visible LEDs irradiation

Abstract

Two D-π-A-type aryl dialkylsulfonium salts with substituted-fluorene as a conjugated system were developed as one-component, versatile photoinitiators under soft irradiation conditions (365–450 nm Light-emitting diodes). The mechanisms for photochemical generation of reactive species (cations and radicals) by the photoinitiators were studied by UV–Vis spectroscopy, theoretical calculations, fluorescence spectroscopy and cyclic voltammetry techniques. The high quantum yields for acid generation (ΦH+ = ∼0.43 to 0.63) of the compounds enable the cationic polymerizations of epoxides and vinyl ether to proceed effectively. Meanwhile, the photocleavage products of sulfoniums (i.e., radicals) initiate the free radical polymerization of acrylate. Such versatile properties allowed them to serve as effective photoinitiators for the synthesis of interpenetrated polymer networks and thiol-ene polymerization without any co-initiators or additives. Based on their beneficial features, these photoinitiators hold great promise for use in photocuring applications.