Change of Temperature and Elastic Stiffness during Dehydration Process of Polyacrylamide Gel

Temporal changes of the weight, volume, temperature and elastic properties during the dehydration process of a polyacrylamide (PAAm) gel were studied. Both the weight and the volume monotonically decreased in the early stage of the process and then tended to saturate in the late stage. At the crossover point between these two dependencies, the temperature of the gel and its elastic stiffness showed anomalies, which indicated similar aspects to the glass transition often observed in non-crystalline polymers. The water content in gels is an important factor affecting the transition.