Characterizations of dehydrated polyacrylamide gel and its formation process

Abstract

This chapter puts forward some characterizations on property evolution of the polyacrylamide (PAAm) gel during dehydration process (DP), followed by that of the dehydrated PAAm gel during temperature-increasing process (TIP). During DP, the amplitude of complex elastic stiffness grows around 103 times as large as the initial value and the loss tangent shows a peak around the time when the logarithm of weight showed a bend point (t g'). . During TIP, in DSC measurement, a thermal anomaly is observed at some temperature (t g'), where the storage modulus decreases remarkably and the loss modulus shows a peak. Besides, intensity of the low-lying Raman peak decreases remarkably with increasing temperature. Because these features resemble those commonly observed around the glass transition in noncrystalline polymers, the similar transition in the dehydrated gel around T is confirmed. However, a difference between the spectral change of the dehydrated gel and that of usual glasses during TIP is also described; the low-lying Raman peak in the dehydrated PAAm gel can be still distinguished even far above T.