Dehydration behaviours of isopropyl group initiate the surface wettability transition of temperature sensitive poly(N-isopropylacrylamide) hydrogel

As a new generation of smart materials, poly(N-isopropylacrylamide) (PNIPAM) is studied for its wettability transition mechanism, which is necessary for the development of the next generation of wettability transition materials. Herein, we minutely report the effects of temperature on the wettability of solid-oil-water and solid-water-air interfaces for the first time. The PNIPAM hydrogel surface (PHS) became less hydrophilic and less lipophobic with the temperature increasing, and the sharply changes in wettability occur range from 28 degrees C to 32 degrees C. Furthermore, unlike previous assumptions, our data about resonance Raman spectroscopy and molecular dynamics simulation suggest that dehydration of isopropyl is more likely to be a cause of drastic changes in wettability. This study suggests a novel foundation to comprehend the wetting behavior of smart PNIPAM gelation surface.