Swelling behavior of polyacrylamide gels in water/acetonitrile system is examined. The linear swelling ratio of the gels decreases with increasing temperature when the water content of the mixtures is low but increases with increasing temperature for the gel in pure water. At high temperatures, the swelling ratio increases with increasing water content of the mixtures. On the other hand, swelling ratio at low temperatures shows interesting behavior: The temperature dependence curves of the linear swelling ratio became convergent for the gels in the mixed solvents, and the data points obtained in the phase-separated circumstances are well superimposed to form a single curve, which can be explained by the Gibbs phase rule. A drastic change occurs in solvent composition inside the gel as well as in the gel volume by cooling, which corresponds to a crossover from collapsed to swollen state of the polymer gels.

中文翻译：

---

聚丙烯酰胺凝胶在水/乙腈混合物中在溶剂相分离温度下的溶胀行为

研究了聚丙烯酰胺凝胶在水/乙腈体系中的溶胀行为。当混合物的含水量较低时，凝胶的线性溶胀比随着温度的升高而降低，而在纯水中，凝胶的线性溶胀比随着温度的升高而增加。在高温下，溶胀比随着混合物含水量的增加而增加。另一方面，低温下的溶胀率表现出有趣的行为：线性溶胀率的温度依赖性曲线在混合溶剂中的凝胶变得收敛，并且在相分离情况下获得的数据点很好地叠加形成单曲线，这可以用吉布斯相位规则来解释。通过冷却，凝胶内部的溶剂组成以及凝胶体积发生剧烈变化，