Star Polymers via Cross-Linking Amphiphilic Macroinitiators by AGET ATRP in Aqueous Media

Amphiphilic star polymers with low polydispersity (PDI) and high molecular weight were synthesized by an activator generated by electron transfer atom transfer radical polymerization (AGET ATRP) in aqueous dispersed media using a simple arm-first method and linear block copolymers poly(ethylene oxide)-b-polystyrene (PEO-PS-Cl) as arm precursors. The amphiphitic block copolymers PEO-PS-Cl with halogen chain-end functionality formed micelles in water and then were cross-linked by the divinyl, cross-linkers. Due to the formation of cross-linker swollen micelles before the polymerization was initiated, star-star or star-linear chain reactions were not required for the star formation. The suppressed star-star coupling reactions resulted in the formation of star polymers with low PDI (M-w/M-n < 1.1) but still high molecular weight (over 1000 kg/mol).