Thermal Behavior, Structure, and Dynamics of Water Confined in Mesoporous Silica Glass and Polymer Gel
Thermal Behavior, Structure, and Dynamics of Water Confined in Mesoporous Silica Glass and Polymer Gel
复制标题
介孔二氧化硅玻璃和聚合物凝胶中限制水的热行为、结构和动力学
DOI：
10.11311/jscta.49.3_95
复制
发表时间：
2022
期刊：
影响因子：
--
通讯作者：
山口 敏男
中科院分区：
文献类型：
--
作者：
吉田 亨次;山口 敏男
由于约束效应和与孔壁的相互作用，多孔材料中受约束的水的性质不同于体水的性质。采用差示扫描量热法（DSC）、x射线散射和中子散射研究了水在介孔二氧化硅（MCM-41）和聚合物凝胶（Sephadex G15）中的热行为、结构和动力学。孔隙直径为21 Å的MCM-41中的水即使冷却到180k也不会冻结。而水的四面体网状结构（冰状结构）是在低温下形成的。此外，承压水与MCM-41孔的亲水性表面有强烈的相互作用。未冻结水的动力学表现出从非Arrhenius型行为向Arrhenius型行为的交叉，暗示了液-液相变。与MCM-41不同，Sephadex G15具有较宽的孔径分布。因此，聚合物凝胶中的水有三种状态：自由水、可冻结合水和未冻水。与多孔二氧化硅相比，G15凝胶中的水分子与凝胶基质的羟基结合更强。
The properties of water confined in porous materials are different from those of the bulk due to the confinement effect and the interaction with the pore wall of the material. The thermal behavior, structure, and dynamics of water confined in mesoporous silica (MCM-41) and polymer gel (Sephadex G15) were investigated by differential scanning calorimetry (DSC), X-ray scattering, and neutron scattering, respectively. Water confined in MCM-41 with a pore diameter of 21 Å does not freeze even when it is cooled to 180 K. However, the tetrahedral-like network structure of water (ice-like structure) is developed at a low temperature. Furthermore, confined water strongly interacts with the hydrophilic surface of MCM-41 pore. The dynamics of the unfrozen water shows a crossover from non-Arrhenius type behavior to Arrhenius type one, implying a liquid-liquid phase transition. Sephadex G15 has a wide pore size distribution unlike MCM-41. Hence, there are three states of water in the polymer gel: free water, freezable bound water, and unfrozen water. Water molecules in G15 gels are more strongly bound to the hydroxyl groups of the gel matrix compared with the case of the porous silica.