Thermal Properties of the Water Confined within Nanopores of Silica MCM‐41
Thermal Properties of the Water Confined within Nanopores of Silica MCM‐41
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DOI：
10.1063/1.2897812
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发表时间：
2008-02
期刊：
影响因子：
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通讯作者：
M. Oguni;Y. Kanke;S. Namba
中科院分区：
文献类型：
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作者：
M. Oguni;Y. Kanke;S. Namba
对限制在直径为1.2、1.6和1.8 nm的二氧化硅MCM-41的孔内的水进行绝热量热法。玻璃化转变被发现在Tg = 115和165 K在1.2 nm的情况下，117，165，和205 K在1.6 nm，和118和210 K在1.8 nm，分别。Tg = 115-118 K的相变是由于位于孔壁的水分子与硅醇基团相互作用的重排冻结引起的，而Tg = 165和205-210 K的相变是由于位于孔中心的水分子的重排冻结引起的。在115 ~ 165 ~ 210 K范围内，随着孔径的增大，玻璃化转变温度呈离散性增加。这表明Tg以及重排的活化能与氢键网络的发展以及每个水分子形成的氢键数量密切相关。结果表明，本体水在Tg = 210 K而不是在136和165 K经历玻璃化转变。
Adiabatic calorimetry was carried out of the water confined within the pores of silica MCM‐41 with diameters of 1.2, 1.6, and 1.8 nm. Glass transitions were found at Tg = 115 and 165 K in the 1.2 nm case, 117, 165, and 205 K in the 1.6 nm, and 118 and 210 K in the 1.8 nm, respectively. The transition at Tg = 115–118 K was interpreted as caused by the freezing of the rearrangement of the water molecules located on the pore wall and interacting with silanol groups, and those at Tg = 165 and 205–210 K of the water molecules located in the center of the pores. It was noticed that the Tg increased discretely with increasing the pore diameter from 115 to 165 to 210 K. This indicates that the Tg and therefore the activation energy for the rearrangement are strongly connected with the development of the hydrogen‐bond network and furthermore the number of the hydrogen bonds formed by each water molecule. It was suggested that the bulk water undergoes the glass transition at Tg = 210 K rather than at 136 and 165 K ...