Dependence of cross-termination rate on RAFT agent concentration in RAFT polymerization
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Rate retardation is an intrinsic property of reversible addition-fragmentation chain transfer (RAFT) radical polymerization. One of reasons for this phenomenon is cross-termination reaction between intermediate radicals and other active radicals. With the help of Stationary State Model and experimentally controlling on k t,cross , the kinetics of styrene RAFT polymerization were performed at different concentrations of RAFT agent. Results show that there is a difference in two effects of cross-termination rate coefficient and concentration of intermediate radicals on cross-termination at different RAFT agent concentrations: at the low concentration range, the cross-termination reaction is mainly affected by its rate coefficient, and at the high concentration range, the cross-termination reaction is mainly affected by the concentration of the intermediate radicals. It shows that there is an optimal concentrations of RAFT agent for a RAFT polymerization with the least rate retardation by considering the balance between these two effects.
Keywordsreversible addition-fragmentation chain transfer (RAFT) radical polymerization rate retardation cross-termination RAFT agent concentrations intermediate radicals
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© The Polymer Society of Korea and Springer Science+Business Media B.V. 2017