A novel reversible thermo-swelling hydrogel

A novel reversible thermo-swelling gel was prepared from poly(vinyl alcohol)-trimellitate (PVA-T) by crosslinking with ethylene glycol diglycidyl ether (EGDGE). Only in the presence of sulfate anion, this polymer gel showed a significant and reversible swelling behavior with increasing the temperature from 5 to 40°C, and vice versa, probably due to the scission and formation of the inter-and/or intramolecular hydrogen-bondings (HBs) between the carboxyls on the side groups. The involvement of inter-and/or intramolecular HBs for the thermo-swelling behavior was also suggested by a significant dependence on HCl concentration of the swelling degree. In addition, the swelling reversibility and reproducibility were confirmed via the temperature jump between 5 and 40°C, well satisfying for a candidate as a thermosensitive material.