Controllability of radical copolymerization of maleimide and ethyl alpha-(n-propyl)acrylate using 1,1,2,2-tetraphenyl-1,2-bis(trimethylsilyloxy) ethane as initiator

The radical copolymerization of maleimide (MI) and ethyl alpha-propylacryla te was performed using 1,1,2,2-tetraphenyl-1,2-bis(trimethylsilyloxy) ethan e (TPSE) as initiator. The whole copolymerization process might be divided into two stages: in the first stage, the copolymerization was carried out o n the common radical mechanism, the molecular weight of the copolymer incre ased rapidly in much lower conversion (< 85%), and did not depend on the po lymerization time and conversion; in the second stags, molecular weight of the copolymer increased linearly with the conversion and the polymerization time. It was found, however, when the conversion was higher than a certain value, for example, more than 36%, the molecular weight of the copolymer w as nearly unchangeable with the polymerization time and the molecular weigh t distribution was widened. The effect of reaction conditions on copolymeri zation was discussed and the reactivity ratios were calculated by the Kelen -Tudos method, the values were r(MI) = 0.13 +/- 0.03, r(EPA) = 0.58 +/- 0.0 6 for TPSE system and r(MI) = 0.12 +/- 0.03, r(EPA) = 0.52 +/- 0.06 for AIB N system. (C) 2000 John Wiley & Sons, Inc.