Synthesis of well-defined star polymers and star block copolymers from dendrimer initiators by atom transfer radical polymerization

Novel polyarylether dendrimers with 1,3,5-tri(4-hydroxyphenoxy)benzene core, polybenzylether interior, and benzyl 2-bromoisobutyrate surface group (CMGn-Br, n=1–3, with functionality of 6, 12, and 24, respectively) were prepared by convergent procedure. ATRP of tert-butyl acrylate (tBA) and styrene (St) with CMGn-Br dendrimer initiators in the presence of CuBr/pentamethyldiethylenetriamine catalytic system was investigated in detail, and a series of well-defined dendrimer-like star PtBA and PSt with precise arm numbers were synthesized under suitable conditions. The quantitative initiation of the dendrimer initiators was demonstrated by high initiation efficiency, 1H NMR spectra, hydrolysis, and MALLS/SEC approach. Star block copolymers comprising PSt and PtBA segments with low polydispersity (1.08<Mw/Mn<1.18) were also successfully synthesized using functional macroinitiators by block copolymerization. In addition, the thermal properties of the resultant polymers were characterized by DSC and TGA.