Synthesis, characterization, and thermal properties of dendrimer-star, block-comb copolymers by ring-opening polymerization and atom transfer radical polymerization

Novel and well-defined dendrimer-star, block-comb polymers were successfully achieved by the combination of living ring-opening polymerization and atom transfer radical polymerization on the basis of a dendrimer polyester. Star-shaped dendrimer poly(epsilon-caprolactone)s were synthesized by the bulk polymerization of epsilon-caprolactone with a dendrimer initiator and tin 2-ethylhexanoate as a catalyst. The molecular weights of the dendrimer poly(epsilon-caprolactone)s increased linearly with an increase in the monomer. The dendrimer poly(epsilon-caprolactone)s were converted into macroinitiators via esterification with 2-bromopropionyl bromide. The star-block copolymer dendrimer poly(epsilon-caprolactone)-block-poly(2-hydroxyethyl methacrylate) was obtained by the atom transfer radical polymerization of 2-hydroxyethyl methacrylate. The molecular weights of these copolymers were adjusted by the variation of the monomer conversion. Then, dendrimer-star, block-comb copolymers were prepared with poly(L-lactide) blocks grafted from poly(2-hydroxyethyl methacrylate) blocks by the ring-opening polymerization Of L-lactide. The unique and well-defined structure of these copolymers presented thermal properties that were different from those of linear poly(epsilon-caprolactone). (c) 2006 Wiley Periodicals, Inc.