Structural changes of water in a hydrogel during dehydration
Structural changes of water in a hydrogel during dehydration
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DOI：
10.1063/1.3058616
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发表时间：
2009-01-21
影响因子：
4.4
通讯作者：
Ikeda-Fukazawa, Tomoko
中科院分区：
文献类型：
--
作者：
Sekine, Yurina;Ikeda-Fukazawa, Tomoko
通过对聚N，N，-二甲基丙烯酰胺水凝胶的拉曼光谱的研究，探讨了水凝胶脱水过程中水和聚合物网络结构变化的机理。结果表明，随着脱水程度的增加，C = O和O-H伸缩振动模的振动能增加，而CH 3摇摆振动模的振动能减小。在C = O伸缩和CH 3摇摆模式中观察到的能量位移表明，聚合物网络随着脱水而收缩，并在某个点经历玻璃化转变。O-H伸缩模的能量移动归因于水结构随聚合物网络结构的变化而变化。通过将本体水的结构模型应用于O-H伸缩区的光谱，分析了凝胶和干燥的玻璃态聚合物中的局部水结构。结果表明，干燥后的玻璃态聚合物的残余水中，由四个氢键组成的四元水结构增加，表明残余水形成了二维氢键网络。聚合物中的局部水结构可能对解释局部水的性质具有重要意义，例如，矿物裂缝中的水。
Raman spectra of poly-N,N,-dimethylacrylamide hydrogel were measured in order to investigate the mechanism of the structural changes in water and the polymer network during dehydration. The results show that the vibrational energies of the C = O and the O-H stretching modes increase with the extent of dehydration, whereas that of the CH3 rocking mode decreases. The energy shifts observed in the C = O stretching and CH3 rocking modes indicate that the polymer network shrinks with the dehydration and undergoes a glass transition at some point. The energy shifts of the O - H stretching modes are attributed to changes in the water structure with the structural change of the polymer network. By applying a structural model of bulk water to the spectra of the O - H stretching region, the local water structures in the gel and the dried glassy polymer were analyzed. The result shows that a tetragonal water structure consisting of four hydrogen bonds increases in the residual water of the dried glassy polymer, suggesting that the residual water forms a two-dimensional hydrogen-bonded network. The local water structure in a polymer might have important implications for the interpretation of properties of localized water, for instance, water in a mineral crack.