5. 高分子ゲルにおける水の昇温結晶化機構について(平成5年度第39回凍結及び乾燥研究会研究報告)

概要

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A phenomenon of ice crystallization during rewarming observed with a gel made of Sephadex G-25, a kind of cross-linked dextran, and water was investigated by DSC (differential scanning calorimetry). The exotherm due to ice crystallization during rewarming in the DSC scan is always preceded by a drift toward an endothermic direction. It was indicated that the drift cannot be ascribed to a glass transition of the polymer-water system but melting of ice crystals as the extent of the drift is too large for the change in heat capacity due to a glass transition. Further DSC measurements were conducted, where a rewarming scan was interrupted when the exotherm appeared and completed (ca. -8℃), followed by the second cooling to -50℃ and the rewarming. During the second rewarming, the exotherm disappeared and the temperature where the DSC curve begins to drift toward an endothermic direction became higher by several degrees. Different thawing behaviour observed during the first and second rewarmings can be explained by the different size distribution of ice crystals formed in the gel during precedent cooling.
1993-10-20