Kinetics of methyl methacrylate and n‐butyl acrylate copolymerization mediated by 2‐cyanoprop‐2‐yl dithiobenzoate as a RAFT agent

Abstract The RAFT (co)polymerization kinetics of methyl methacrylate (MMA) and n ‐butyl acrylate (BA) mediated by 2‐cyanoprop‐2‐yl dithiobenzoate was studied with various RAFT concentrations and monomer compositions. The homopolymerization of MMA gave the highest rate. Increasing the BA fraction f BA dramatically decreased the copolymerization rate. The rate reached the lowest point at f MMA ∼ 0.2. This observation is in sharp contrast to the conventional RAFT‐free copolymerization, where BA homopolymerization gave the highest rate and the copolymerization rate decreased monotonously with increasing f MMA . This peculiar phenomenon can be explained by the RAFT retardation effect. The RAFT copolymerization rate can be described by 〈 R p 〉/〈 R p 〉 0 = (1 + 2(〈 k c 〉/〈 k t 〉)〈 K 〉)[RAFT] 0 ) −0.5 , where 〈 R p 〉 0 is the RAFT‐free copolymerization rate and 〈 K 〉 is the apparent addition–fragmentation equilibrium coefficient. A theoretical expression of 〈 K 〉 based on a terminal model of addition and fragmentation reactions was derived and successfully applied to predict the RAFT copolymerization kinetics with the rate parameters obtained from the homopolymerization systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3098–3111, 2007