Oxygen-Demanding Photocontrolled RAFT Polymerization Under Ambient Conditions

A photocontrolled reversible addition-fragmentation chain transfer (RAFT) process is developed by initiating polymerization through a 1,3-diaminopropane-triethylborane (DAPTB)-diphenyl iodonium salt (Ph2I+) complex (DAPTB/Ph2I+) under ambient temperature and atmospheric conditions. Upon demand, this air-stable DAPTB/Ph2I+ complex is photolyzed to liberate a reactive triethylborane that consumes atmospheric oxygen and generates ethyl radicals, which initiate and mediate RAFT polymerization. Controlled RAFT polymerization is thus achieved without any prior deoxygenation using a novel RAFT chain transfer agent, BP-FSBC, which contains both benzophenone and sulfonyl fluoride moieties. Furthermore, the kinetics of polymerization reveal that the reaction process is rapid, and well-defined polymers are produced by a 61% conversion of 2-hydroxyethyl acrylate (HEA) within 7 min and 77% conversion of N,N-dimethylacrylamide (DMA) within 10.5 min. The temporal and spatial control of this photopolymerization is also demonstrated by an on/off switch of UV irradiation and a painting-on-a-surface approach, respectively. In addition, active chain ends are demonstrated by preparing block copolymers by chain extension and click sulfur(VI)-fluoride exchange postreaction using RAFT-derived macrochain transfer agents.

Automated summary

This study developed a photocontrolled reversible addition-fragmentation chain transfer (RAFT) process that utilizes photolysis to release a reactive triethylborane for initiating and mediating RAFT polymerization. The controlled polymerization was achieved without prior deoxygenation, and the temporal and spatial control of the photopolymerization was demonstrated. Additionally, active chain ends were demonstrated by preparing block copolymers using RAFT-derived macrochain transfer agents.