Sakai Yuko, Kuroki Shigeki, Satoh Mitsuru
Department of Chemistry and Materials Science, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8550, Japan.
Langmuir. 2008 Jun 1;24(13):6981-7. doi: 10.1021/la800397f. Epub 2008 Jun 7.
The so-called "super-salt-resistive gel", or poly(4-vinylphenol) (P4VPh) hydrogel, of different water contents ( H = 97-51%) was prepared by cross-linking with different amounts of ethylene glycol diglycidyl ether. 1H NMR spectroscopy was used to investigate the dynamic properties of water in the gel samples in terms of the spin-spin relaxation. The T2 values in those hydrogels were analyzed by assuming a two-component system, namely, T 2(long) and T2(short), and their fractions were obtained. In the higher water content region (75% < or = H < or = 97%), T2(long) for P4VPh gel was almost constant or even slightly increased with decreasing temperature. On the other hand, T2(long) for poly(vinyl alcohol) (PVA) gel (80% < or = H < or = 96%) significantly decreased with decreasing temperature, showing a natural behavior for water mobility in common hydrogels. Water in P4VPh gels of lower water contents ( H = 70% and 51%) also showed intriguing behaviors: the T2 values are much larger than those of gels with higher water contents and decreased with decreasing temperature only in the lower temperature range (<10 degrees C). The fraction of T2(long) values of P4VPh gel showed another contrast to those of PVA gel; the latter decreased with decreasing water content (normal behavior), while in the former gel the highest fraction (ca. 60% at 20 degrees C) was observed for a sample with the lowest water content ( H = 51%). On the other hand, the results of DSC measurements for P4VPh gel were less specific than those of T2 and comparable to those of common hydrogels such as PVA; with decreasing water content, the total amounts of free water and freezable bound water per polymer mass (g/g) decreased, while the amount of nonfreezing water per polymer also decreased.
通过与不同量的乙二醇二缩水甘油醚交联制备了具有不同含水量（H = 97 - 51%）的所谓“超耐盐凝胶”，即聚（4 - 乙烯基苯酚）（P4VPh）水凝胶。利用1H NMR光谱通过自旋 - 自旋弛豫研究了凝胶样品中水的动态性质。通过假设双组分体系，即T2（长）和T2（短）来分析那些水凝胶中的T2值，并获得它们的分数。在较高含水量区域（75%≤H≤97%），P4VPh凝胶的T2（长）几乎恒定，甚至随温度降低略有增加。另一方面，聚（乙烯醇）（PVA）凝胶（80%≤H≤96%）的T2（长）随温度降低显著降低，显示出普通水凝胶中水迁移率的自然行为。较低含水量（H = 70%和51%）的P4VPh凝胶中的水也表现出有趣的行为：T2值远大于较高含水量凝胶的T2值，并且仅在较低温度范围（<10℃）随温度降低而降低。P4VPh凝胶的T2（长）值分数与PVA凝胶的分数呈现出另一种对比；后者随含水量降低而降低（正常行为），而在前者凝胶中，对于含水量最低（H = 51%）的样品观察到最高分数（20℃时约为60%）。另一方面，P4VPh凝胶的DSC测量结果不如T2测量结果具体，与PVA等普通水凝胶的结果相当；随着含水量降低，每聚合物质量（g/g）的游离水和可冻结结合水总量减少，而每聚合物的非冻结水量也减少。
