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Abstract
The direct photolysis of reversible addition fragmentation chain transfer (RAFT) agents under visible light was demonstrated by electron spin resonance (ESR) using 5,5-dimethyl-1-pyrroline N-oxide as a typical spin trap. The hyperfine coupling lines obtained by ESR spectroscopy showed the successful capture of the carbon-centered and the sulfur-centered radical. Photo-polymerization of vinyl acetate under different wavelengths was performed to verify the effects of wavelength on the process. The effect of the R group of RAFT agents on the photolysis was investigated by spin-trapping experiments using poly (butyl acrylate) and poly (vinyl acetate) as macroRAFT agents. The quantitative experiment showed the yield of photolysis of a xanthate to be only 0.023% under λ > 440 nm.
Highlights
Visible light has been widely applied in various reversible deactivation radical polymerization (RDRP) [1] techniques, such as nitroxide mediated polymerization (NMP) [2,3,4,5], atom-transfer radical polymerization (ATRP) [6,7,8,9] and reversible addition fragmentation chain transfer (RAFT) [10,11,12]
The second approach is the activation of a RAFT agent using a photoredox catalyst, namely photo-induced electron transfer RAFT (PET-RAFT) polymerization [17], developed by Boyer and co-workers
Proposed mechanism utilizing of visible-light-induced addition fragmentation chain transfer polymerization utilizing direct photolysis of RAFT agents
Summary
Visible light has been widely applied in various reversible deactivation radical polymerization (RDRP) [1] techniques, such as nitroxide mediated polymerization (NMP) [2,3,4,5], atom-transfer radical polymerization (ATRP) [6,7,8,9] and reversible addition fragmentation chain transfer (RAFT) [10,11,12]. The second approach is the activation of a RAFT agent using a photoredox catalyst, namely photo-induced electron transfer RAFT (PET-RAFT) polymerization [17], developed by Boyer and co-workers In this approach, the primary radical is generated by the reduction of a RAFT agent by a photoredox catalyst under visible light irradiation. 1. Proposed mechanism utilizing of visible-light-induced addition fragmentation chain transfer (photo-RAFT) polymerization utilizing direct photolysis of RAFT agents. Has, using this approach, the direct detection of radicals generated by the photo-RAFT process beenisextensively used in such cases. DMPO as a spin trap for the radicals structures of radical adducts based mainly on the hyperfine coupling constants, which are, in general, generated the direct photolysis a RAFTHerein, agent under visibleDMPO light, aiming to prove the direct useful from for distinguishing trappedofradicals. Generated from the direct photolysis of a RAFT agent under visible light, aiming to prove the direct photoactivation process (Scheme 2).
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