Introduction of stimuli-responsive polymers into regenerated cellulose film by means of photografting

Photografting (λ>300 nm) of methacrylic acid (MAA) and N-isopropylacrylamide (NIPAAm) on regenerated cellulose film (thickness=20 μm) was carried out in water solvent. Xanthone was used as a photoinitiator by coating it on the film sample. The percentage of grafting of both monomers increased with an increase in the concentration of xanthone. Distribution of the grafted chains in the resultant MAA-grafted film was examined by an electron probe microanalysis and an attenuated total reflection infrared spectroscopy. The grafted chains were found to distribute inside the film irrespective of the polymerization conditions such as the xanthone concentration (0.1 and 0.5 wt.%) and the polymerization temperature (40°C and 60°C). The MAA-grafted film shrank in acidic medium, while it swelled in alkaline region, showing a pH- responsive character, which was not influenced by the polymerization conditions. On the other hand, NIPAAm-grafted film exhibited a temperature-responsive character, where it swelled and shrank in water lower and higher than around 30°C, respectively. The pH- and temperature-responsive characters of grafted films increased with increasing the percentage of grafting.