Naphthalimide derivatives containing benzyl-sulfur bond as cleavable photoinitiators for near-UV LED polymerization

Abstract

Three naphthalimide aryl benzyl sulfide derivatives (NABSs) cleavable photoinitiators (PIs) containing benzyl-sulfur bonds were designed and prepared. The effect of the benzyl-sulfur moiety and substituents located on benzene ring of the benzyl group on photochemical behavior, involving the light absorption properties, potential mechanisms of the photolysis of NABSs under UV LED at 405 nm, and the electron transfer reaction between NABSs and diphenyliodonium hexafluorophosphate (Iod) were investigated in detail. The NABSs have different photolysis mechanisms as compared to PIs containing only an aryl-sulfur bond. NABS3 is most efficient for initiating free radical photopolymerization of acrylate monomers under UV LED exposure at 405 nm. Furthermore, NABSs/Iod systems can initiate the cationic photopolymerization of epoxides. Interestingly, the polymers prepared by using NABSs as the PI exhibit a great photoluminescence band at about 460 nm under UV LED irradiation at 405 nm.