Preparation and thermally induced adhesion properties of a poly(vinyl alcohol)-g-N-isopropylacrylamide copolymer membrane

In the work described here, poly(vinyl alcohol)-g-N-isopropylacrylamide was prepared via graft polymerisation of N-isopropylacrylamide (NIPAM) onto poly(vinyl alcohol) (PVA). The structure and components of the polymer were characterised by differential thermogravimetry (DTG), differential scanning calorimetry (DSC), 1H nuclear magnetic resonance spectroscopy (1H NMR) and fourier transform infrared spectroscopy (FT-IR) testing, respectively. The T-type peel adhesion strengths and water contact angles of the prepared graft copolymer membranes were determined at different temperatures. The results indicated that the membrane has an obvious change in adhesion and water contact angle around the lower critical solution temperature (LCST) of the thermosensitive PNIPAM, regardless of the composition of the copolymers. Based on the scanning electron microscope (SEM) and energy dispersive spectrometric (EDS) analysis of freeze-dried graft copolymer membranes swollen in water at various temperatures, a mechanism for the thermally induced adhesion properties of the graft copolymer was proposed.