Abstract: | The melting temperatures (TM) of hydrogels prepared by chilling aqueous solutions of syndiotacticity-rich poly(vinyl alcohol) (s-PVA) at 0°C were measured rising temperature of gels from the initiative temperature (TI) of 0–70°C (every 10°C). The apparent enthalpies of fusion of a junction ΔH's were estimated from the relation between the logarithm of polymer concentration (log C) and 1/TM. ΔH depended on TI, showing that the melting point of gels depended on a thermal hysteresis. The highest polymer concentration CH in those of the gels which have no melting point above an initiative temperature was determined and ΔH was estimated from the relation between log CH and the reciprocal melting point of the gels with CH, 1/TIM. The ΔH was 15.1 kJ/mol in the range of higher polymer concentrations and 43.9 kJ/mol in the range of lower concentrations. |