Photocontrolled cationic degenerate chain transfer polymerizations via thioacetal initiators

Abstract

Recent developments in photocontrolled polymerizations have facilitated the development of previously inaccessible materials. While photocontrolled radical polymerizations have been extensively studied, related processes involving cationic polymerizations are underexplored and limited to RAFT processes. In this study, we disclose a visible light, temporally controlled cationic polymerization of vinyl ethers utilizing thioacetals and a photoredox catalyst. We demonstrate a broad scope of thioacetal initiators that achieve a well-controlled polymerization by recapping propagating chains via photocatalyst turnover in combination with a degenerate chain transfer process through sulfonium intermediates. Furthermore, we show that a photocatalyst with a more reducing ground state reduction potential allows for enhanced control and excellent temporal regulation of polymerization.