Preparation of nano‐sized poly(ethylene oxide) star microgels via reversible addition‐fragmentation transfer polymerization in selective solvents

Poly(ethylene oxide) (PEO) star microgels with a cross‐linked polystyrene core were successfully prepared by reversible addition‐fragmentation transfer polymerization of styrene (St) and divinylbenzene (DVB) with dithiobenzoate‐terminated PEO monomethyl ether (DTB‐MPEO) as macro chain transfer agent in mixtures of ethanol and tetrahydrofuran (THF). The formation of star polymers was affected by polymerization time, solvents and St:DVB:DTB‐MPEO molar ratios. Narrow polydispersed star microgels with high molecular weight were obtained under appropriate polymerization conditions. Transmission electron micrographs suggest that PEO star polymers could form nano‐size spherical micelles in mixtures of water and THF, which further demonstrates the amphiphilic nature of the star polymers.