Preparation of hyperbranched polymers by self-condensing vinyl radical polymerization

A novel acrylic AB* monomer, 2- (2-chloroacetyloxy) -ethyl acrylate (CAEA), was prepared from 2-hydroxyethyl acrylate with chloroacetyl chloride in th e presence of triethylamine. The self-condensing vinyl polymerization of CA EA and CAEA with styrene catalyzed by the complex of CuCl/2,2'-bipyridyl ha s been studied. Hyperbranched polymers and copolymers containing ester grou ps in the main chain were prepared from radical polymerization. All the pol ymerization products were characterized by H-1-NMR. It has been proved that CAEA exhibits distinctive polymerization behavior. During the initial stag e of the polymerization, molecular weight of the polymer formed increases e xponentially with polymerization time, and then the increase rate slows dow n. However, a significant amount of monomer remains present throughout the polymerization consistent with typical chain polymerization. Also, if a muc h longer polymerization time was used, the polymerization system became gel . As a result of the unequal reactivity of the primary ester halide and the secondary ester halide, the polymerization is different from an ideal self -condensing vinyl polymerization: the branch structures of polymers prepare d depend dramatically on the ratio of 2,2'-bipyridyl to CAEA. Hyperbranched polymers and copolymers exhibit improved solubility in organic solvent. Ho wever, they have some lower thermal stability compared with their linear an alogs. (C) 2001 Elsevier Science Ltd. All rights reserved.