Poly(N-isopropylacrylamide-co-sodium acrylate) copolymer brushes graftedon SiO2-coated quartz crystal surface were prepared with a surface-immobilizedinitiator. The collapse and swelling of the thermally sensitive copolymer brushes inwater were studied with quartz crystal microbalance in situ. The frequency and dissipationchanges with the temperature increasing in the range 20–38 8C indicate thatthe brushes undergo a continuous collapse transition. Our results show that thecopolymer brushes collapse to a state where the brushes were prepared. A hysteresiswas observed in the cooling process. Fourier transform infrared (FTIR) resultsrevealed that the formation of some additional hydrogen bonds within the copolymerchains at their collapsed state is responsible for the hysteresis.
