Ionic liquid-mediated synthesis and self-assembly of poly(ethylene glycol)-block-polystyrene copolymer by ATRP method

Poly(ethylene glycol)-block-polystyrene (PEG-b-PS) was synthesized by the atom transfer radical polymerization of styrene using PEG-Br as the macroinitiator in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]). CuBr and 2,2aEuro(3)-bipyridyl were used as the catalyst and ligand, respectively. The structure, composition, and molecular weight of the PEG-b-PS copolymer were characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, and gel permeation chromatography. The PEG-b-PS copolymer with a high molecular weight (M (n) = 51,000 g mol(-1)) and relatively low polydispersity index (PDI = 1.35) was formed at 110 A degrees C for 5 h. Self-assembly of this amphiphilic block copolymer in toluene at different concentrations and in dimethylformamide (DMF)/water systems was also examined. Transmission electron microscopy showed that the block copolymer formed different morphologies spontaneously according to the different solvent systems used.