Radical copolymerisation propagation kinetics of methyl ethacrylate and styrene

Pulsed-laser polymerisation has been used to investigate the radical copolymerisation kinetics of styrene with methyl ethacrylate. Experiments were conducted over the temperature range 30-80°C. The results for copolymer composition and the average propagation rate coefficients, 〈k_p〉, can be interpreted using terminal model kinetics. It is argued that the primary factor influencing the copolymerisation 〈k_p〉 data is the sterically hindered methyl ethacrylate radicals and this steric effect swamps any enthalpic penultimate unit effect which may be expected to play a role in the copolymerisation reaction. The terminal model reactivity ratios are a strong function of temperature and this reflects the importance of depropagation reactions at higher temperatures and lower concentrations of methyl ethacrylate.