Controlled radical polymerization of styrene and methyl acrylate in the presence of reversible addition–fragmentation chain transfer agents,phenylethyl phenyl dithioacetate and phenyldithioacetic acid

The use of phenyldithioacetic acid (PDA) in homopolymerizations of styrene or methyl acrylate produced only a small fraction of chains with dithioester end groups. The polymerizations using 1‐phenylentyl phenyldithioacetate (PEPDTA) and PDA in the same reaction showed that PDA had little or no influence on the rate or molecular weight distribution even when a 1:1 ratio is used. The mechanistic pathway for the polymerizations in the presence of PDA seemed to be different for each monomer. Styrene favors addition of styrene to PDA via a Markovnikov type addition to form a reactive RAFT agent. The polymer was shown by double detection SEC to contain dithioester end groups over the whole distribution. This polymer was then used in a chain extension experiment and the M_n was close to theory. A unique feature of this work was that PDA could be used to form a RAFT agent in situ by heating a mixture of styrene and PDA for 24 h at 70 °C and then polymerizing in the presence of AIBN to give a linear increase in M_n and low values of PDI (<1.14). In the case of the polymerization of MA with PDA, the mechanism was proposed to be via degradative chain transfer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5232–5245, 2005