writer：Tianzhu Zhang*, Ting Li, Erik Nies, Hugo Berghmans, and Liqin Ge*
keywords：PVME, Isothermal crystallization, Differential scanning calorimetry (DSC)
source：期刊
specific source：Polymer, 2009, 50: 1206–1213
Issue time：2008年
A study on the isothermal crystallization of water in aqueous solutions of poly(vinyl methyl ether) (PVME) was carried out by the differential scanning calorimetry (DSC). The influence of PVME concentration (49.5, 44.5 and 39.5 v%) and the crystallization temperature (Tc) on crystallization rate G, crystallization enthalpy (DHc) and melting enthalpy (DHm) was investigated. Avrami equation cannot be used to describe the crystallization process of water in aqueous PVME solution. Within the measured
temperature range, the crystallization rate G increases with the crystallization temperature Tc and with the decreasing PVME content. The crystallization enthalpy DHc linearly increases with the degree of supercooling. The influence of Tc on the DHc becomes more marked with increasing PVME concentration. For 49.5 and 44.5 v% PVME solutions, the amount of water arrested in solution during the isothermal
crystallization and the final concentration of PVME-rich phase increase linearly with the Tc, whereas for 39.5 v% PVME solution, these two values almost do not change with Tc. The amount of frozenwater in the subsequent cold crystallization is approximately proportional to the initial Tc. The approximately constant DHm for a given concentration at the different initial isothermal crystallization temperatures
suggests that the total amount of ice from the first isothermal crystallization and the second cold crystallization is same. The quantitative relation of the amount of frozen water in the cold crystallization and the initial Tc demonstrates that PVME/water complexes are thermodynamically unstable.