Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8551, Japan.
J Phys Condens Matter. 2010 Sep 15;22(36):365105. doi: 10.1088/0953-8984/22/36/365105. Epub 2010 Aug 20.
Glass transition behaviors of dilute aqueous solutions are currently unclear because the water crystallizes immediately below the fusion temperatures to prevent the determination. The behaviors of methanol aqueous solutions [(CH(3)OH)(x)(H(2)O)(1 - x)] were studied here by confining the solutions within silica-gel pores and following the enthalpy relaxation associated with the glass transitions by adiabatic calorimetry. The dilution of the solutions in the composition range x < 0.3 brought both abrupt increase in the glass transition temperature T(g) as referred to the composition dependence expected from the behavior in x > 0.3 and appearance of a new glass transition at around 115 K. It was conjectured from the results that a hydrogen-bond network inherent to water starts to develop at around x = 0.3, and that molecules on the pore wall cannot join the network by forming tetrahedrally extended hydrogen-bonds so that they should constitute a mobile layer as an interfacial one. Such a special layer is understood as absent above x > 0.3, indicating that no network structure inherent to water is developed in the solutions.
稀水溶液的玻璃化转变行为目前尚不清楚，因为水在熔融温度以下立即结晶，从而阻止了测定。本文通过将甲醇水溶液[(CH(3)OH)(x)(H(2)O)(1 - x)]限制在硅胶孔内，并通过绝热量热法跟踪与玻璃化转变相关的焓弛豫，研究了其行为。在组成范围 x < 0.3 下，溶液的稀释导致玻璃化转变温度 T(g)突然升高，这与 x > 0.3 时的预期行为有关，并且在 115 K 左右出现了新的玻璃化转变。从结果推测，水固有的氢键网络在大约 x = 0.3 时开始发展，而孔壁上的分子不能通过形成四面体延伸氢键加入网络，因此它们应该构成一个作为界面的移动层。在 x > 0.3 以上不存在这样的特殊层，表明溶液中没有水固有的网络结构。
