Synthesis of amphiphilic star block copolymers of polystyrene with PEG core via ATRP-control of chain architecture and the formation of core-shell type globular structure

Amphiphilic star block copolymers made of poly(ethylene glycol) (PEG) core and branched PS arms having controlled chain lengths and numbers were synthesized by atom transfer radical copolymerization (ATRP) of styrene and chloromethylstyrene (CMS) in the presence of tetrafunctional PEG macroinitiator. The chain lengths and number of PS chains were controlled by adjusting the initial feed ratio of CMS to styrene and CMS to hydrophilic tetrafunctional macroinitiator, respectively, for a given polymerization time. The obtained polymers have well defined and controlled architectures. Use of excess amount of CMS and longer reaction time leads to the synthesis of dendrimer like amphiphilic block copolymer having four hyperbranched polymer arms, whose shape is closer to globular core-shell structure compared to general star shape polymers.