Phase Transition of pNIPAM Grafted on Plasma-Activated PEO Monitored in-Situ by Quartz Crystal Microbalance

Thermoresponsive poly(N-isopropylacrylamide) layers were grafted on plasmaactivated poly(ethylene oxide)-like substrate. Analysis by ToF-SIMS confirmed the presence of a pNIPAM film, which shows a phase transition temperature at 28 - 32 °C with hysteresis, as determined in-situ by quartz crystal microbalance. During the transition, the frequency of the pNIPAM coated quartz sensor exhibits a pronounced and unexpected minimum while the dissipation changes monotonously. This peculiar behaviour is explained by temporary formation of water-rich regions, which may cause delayed release and uptake of water during the collapse and re-swelling of the layer.JRC.I.4-Nanotechnology and Molecular Imagin