AGING OF POLY(VINYL ALCOHOL) GELS PREPARED FROM DIMETHYLSULFOXIDE WATER SOLUTIONS

In order to elucidate the structure of poly(vinyl alcohol) (PVA) gels, the gels studied were aged for as long as 500 days at 30-degrees-C. The original gel was formed from PVA solutions in a mixed solvent of dimethylsulfoxide (DMSO) and water by chilling at -34-degrees-C for one day. The aged gel was shown to have a well grown crystal phase, in that the melting endotherm from differential scanning calorimetry could be clearly separated into two or three components, which were named A, B and C, in order of melting temperature. The enhancement of the gel modulus and the solvent exclusion observed in the aged DMSO/water gels could be attributed to phase separation, which facilitates crystallization into the B and C components. The A component was shown not to bear a strong relationship to the high modulus and the exclusion of solvent, although it may be the most common crystallite grown from PVA solutions.