Mechanism and Kinetics of RAFT-Based Living Radical Polymerizations of Styrene and Methyl Methacrylate (ORGANIC MATERIALS CHEMISTRY-Polymeric Materials)

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The bulk polymerizations of styrene and methyl methacrylate in the presence of model polymerdithiocarbonate adducts as mediators and benzoyl peroxide (BPO) as a conventional initiator were kinetically studied. The polymerization rate, hence the concentration of polymer radical P , was proportional to [BPO]1/2. The pseudo-first-order activation rate constants kact were determined by the GPC peak-resolution method. The results showed that kact is directly proportional to [P ], indicating that reversible addition-fragmentation chain transfer (RAFT) is the only important mechanism of activation. The magnitude of the exchange rate constant kex (= kact/[P ]) was strongly dependent on both the structures of the dithiocarbonate group and the polymer. The kex values for the three RAFT systems examined in this work were all very large, explaining why these systems can provide low-polydispersity polymers from an early stage of polymerization.