Synthesis of Triblock Copolymer Having Alternating Structures and Kinetics Study on RAFT-Mediated Bulk, Miniemulsion and Seed Miniemulsion Polymerizations

We have conducted reversible addition-fragmentation chain transfer (RAFT) polymerizations of styrene (St) and maleic anhydride (MAh) and n-butyl acrylate (BA) to produce a well-defined triblock copolymer having alternating structure, P(St-alt-MAh)-b-PSt-b-PBA, via bulk, miniemulsion and seed miniemulsion polymerizations. The polymerization kinetics and living characters were investigated. The results followed by gel permeation chromatography (GPC) showed that bulk and miniemulsion polymerizations exhibited controlled nature such as narrow polydispersity index (PDI), controlled molecular weight, and first-order polymerization kinetics, whereas triblock copolymer owned a rather wider PDI. Comparison of GPC RI and UV traces revealed that alternating copolymer and diblock copolymer have a very high percentage of living chains. For seed miniemulsion polymerization, when the molecular weight of triblock copolymer is more than 36,000 g/mol, the formation of homopolymer of BA resulted in broadening of PDI. (1)H NMR method was used to identify the compositions of block copolymers. Differential scanning calorimetry analysis showed that the copolymers exhibited distinct glass temperatures. POLYM. ENG. SCI., 51: 1041-1050, 2011. (C) 2011 Society of Plastics Engineers