Nondiffusion-Controlled Photoelectron Transfer Induced by Host–Guest Complexes to Initiate Cationic Photopolymerization

Two novel supramolecular photoinitiators (supra-photoinitiators) based on the host–guest complexation of macrocycles (pillar[6]arene, P6; prism[5]arene, NP5) and diphenyl-iodonium salt (Iod) were fabricated. Under light irradiation, macrocycle P6 or NP5 could donate electrons to the guest molecule Iod, which generated highly active free radicals and cationic fragments to achieve efficient polymerization. Compared to a commercial activator, the electron transfer between macrocycles and Iod were under nondiffusion control, endowing a much higher photopolymerization rate and epoxy resin final conversion. In addition, the host–guest complexation of NP5 extended the initiating wavelength of Iod from ultrashort ultraviolet to near-ultraviolet, which could better match the environment-friendly LED light source. It is anticipated that a supra-photoinitiator may open a new route for designing novel photoinitiators with high performance.