Temperature controlled cationic photo-curing of a thick, dark composite

Abstract

In this research, the cationic photopolymerization of 1,4-butanediol diglycidyl ether was found to have an infinitely long induction period due to the sustained stability of the secondary oxonium ions species at low temperature. Based on this, the system could be separated into two steps: photolysis of the photoinitiator without polymerization under irradiation and polymerization in the dark. Under irradiation, only the secondary oxonium ion species was generated at low temperature, whereas the polymerization could proceed and auto-accelerate at room temperature without irradiation. The two steps could be monitored by a significant change of the temperature. The temperature controlled cationic mechanism resolved the issue of light penetration in colored thick composites. Through temperature control, the infinitely thick and dark material could be prepared by cationic photopolymerization.