Multibrominated Hyperbranched Polymers: Synthesis and Further Functionalizations by ARGET ATRP or Click Chemistry

Hyperbranched polymers with multiple alkyl bromide peripheral groups were synthesized by the copolymerization of styrene with ethylene glycol dimethacrylate (2.5, 5.0, 7.5, or 10.0 mol% relative to styrene) in the presence of CBr4 (1020-fold excess vs. the radical initiator). The latter compound markedly delayed the gelation and served as the source of terminal bromine atoms via transfer to the propagating radicals. The degree of branching increased with the amount of crosslinker. The alkyl bromide groups were used in further chemical modifications (ATRP at low catalyst concentration or azidation with NaN3 followed by CuBr-catalyzed click coupling of an alkyne-terminated polymer) that yielded star copolymers with hyperbranched cores.