Synthesis of thermoresponsive polystyrene-based comb-type grafted poly( N -isopropylacrylamide)

Narrowly distributed polystyrene-g-p(N-isopropylacrylamide) (PSt-g-PNIPAM) was prepared by atom transfer radical polymerization (ATRP) of N-isopropylacrylamide using the brominated polystyrene as macroinitiator and CuCl combined with hexamethyltriethylenetetramine as catalyst. Fourier transform infrared (FT-IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy confirmed the structure of PSt-g-PNIPAM. The gel permeation chromatography (GPC) showed that the graft copolymer had a single distribution peak with molecular weight, M _n (g/mol) of 19815 g/mol (using polystyrene as the standard). Differential scanning calorimetry (DSC) revealed that due to both effects of hydrophobic isopropyl groups and hydrogen bonds in the amide group, the glass transition temperature (T _g) of PSt-g-PNIPAM enhanced 16.0°C compared to the T _g of the polystyrene.