Synthesis of Star Block Copolymers from Dendrimer Initiators by Combining Ring-Opening Polymerization and Atom Transfer Radical Polymerization

Abstract

Well-defined dendrimer-like star block copolymers up to 24 arm were successfully achieved by combination of living ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP) on the basis of poly(aryl ether) dendrimers (CMGn-OH, n = 1−3, with functionality of 6, 12, and 24, respectively). Star polylactides (CMGn-PLLA) were synthesized by bulk polymerization of l-lactide with multifunctional dendrimer initiators and stannous octoate catalyst. The molecular weights of CMGn-PLLA increased linearly with increasing monomer conversion, with molecular weight distributions remaining below 1.15, indicating the living nature of polymerization. CMGn-PLLA was converted into a macroinitiator CMGn-PLLABr via esterification with 2-bromoisobutyryl bromide. ATRP of methyl methacrylate (MMA) and styrene (St) using the CMGn-PLLABr/CuBr/pentamethyldiethylenetriamine initiating system afforded star block copolymers with predetermined molecular weights and narrow molecular weight distributions (1.05 < Mw/...