Studies on the atom transfer radical polymerization of a maleimide AB* monomer and modification of the halogen end groups

The atom transfer radical polymerization (ATRP) of an AB* monomer, N-(4-α-bromobutyryloxy phenyl)maleimide (BBPMI), was conducted using the complex of CuBr/2,2′-bipyridine as catalyst. The study of kinetics of polymerization and the growth behavior of macromolecules show that the polymerization proceeds rapidly in first 1 h and then slows down. The decrease in the rate of polymerization is ascribed to the poor reactivity of maleimide radicals from A* to initiate the polymerization of maleimide double bonds. The molecular weight of the resulting polymer also increases with the dosage of catalyst. The coincidence of molecular weight determined by hydrogen proton nuclear magnetic resonance spectroscopy (¹H NMR) and gel permeation chromatography (GPC) proves that the resulting polymer is of linear structure, which is further verified by ¹³C NMR measurement and high performance liquid chromatography (HPLC) analysis of the hydrolysate of the resulting polymer. The stabilization modification of the halogen end groups of the resulting polymer by free-radical chain transfer reaction was attempted under ATRP condition. Isopropyl benzene was employed as the chain transfer agent. Indeed, the modified polymer with carbon-bromine bonds conversion of 40.7% shows enhanced thermal stability. The initial weight loss temperature has been increased from 193 to 243 °C. On the other hand, the atom transfer radical copolymerization of BBPMI with styrene resulted in the formation of hyperbranched polymer.