Water and moisture uptake by plasma polymerized thermoresponsive hydrogel films

Water and moisture uptake characteristics of plasma polymerized N-isopropylacrylamide (pNIPAAm) hydrogel films, deposited under different reactor process conditions, have been studied using a quartz crystal microbalance with dissipation monitoring. Trends in frequency and dissipation values during water/moisture sorption studies indicated that the pNIPAAm thin films were thermoresponsive. Deposition at higher substrate temperatures and lower reactor pressures, where electron and ion temperatures are high, yielded films with relatively high moisture uptake capacity under ambient humidity conditions. In contrast, pNIPAAm films deposited at lower substrate temperatures and higher pressures, where cross-link densities are reduced, showed relatively low moisture uptake. These results are consistent with the hydrogen-bonding characteristics of the pNIPAAm films.