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 the presence of triethylamine. The self-condensing vinyl polymerization of CAEA and CAEA with styrene catalyzed by the complex of CuCl/2,2′-bipyridyl has been studied. Hyperbranched polymers and copolymers containing ester groups in the main chain were prepared from radical polymerization. All the polymerization products were characterized by 1H-NMR. It has been proved that CAEA exhibits distinctive polymerization behavior. During the initial stage of the polymerization, molecular weight of the polymer formed increases exponentially with polymerization time, and then the increase rate slows down. However, a significant amount of monomer remains present throughout the polymerization consistent with typical chain polymerization. Also, if a much 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 prepared depend dramatically on the ratio of 2,2′-bipyridyl to CAEA. Hyperbranched polymers and copolymers exhibit improved solubility in organic solvent. However, they have some lower thermal stability compared with their linear analogs.