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, 〈kp〉, can be interpreted using terminal model kinetics. It is argued that the primary factor influencing the copolymerisation 〈kp〉 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.