Hydrogel, a three-dimensional elastic structure of cross-linked polymer chains, swells or deswells when immersed in aqueous organic solutions. The swelling of hydrogels depends on temperature, solvent composition, and hydrogel structure as the thermodynamic driving forces for hydrogel swelling are due to solvent – hydrogel interactions and expansion of elastic network. In this work, polymer Nonrandom Two-Liquid activity coefficient model is used to account for the solvent – hydrogel interactions and a semi-empirical expression for rubber elasticity is used to describe the expansion of elastic network. The model successfully correlates data for both swelling and equilibrium phase compositions for n-isopropyl acrylamide hydrogels in water – ethanol, water – acetone, water – n-butanol, and water – methyl isobutyl ketone mixed solvents.

水凝胶是一种交联的聚合物链的三维弹性结构，浸入有机水溶液后会溶胀或消溶。水凝胶的溶胀取决于温度，溶剂组成和水凝胶的结构，因为水凝胶溶胀的热力学驱动力是由于溶剂-水凝胶的相互作用和弹性网络的扩张而引起的。在这项工作中，聚合物非随机两液活度系数模型用于解释溶剂-水凝胶相互作用，橡胶弹性的半经验表达式用于描述弹性网络的扩展。该模型成功地关联了n-异丙基丙烯酰胺水凝胶在水–乙醇，水–丙酮，水– n中的溶胀相和平衡相组成的数据。-丁醇和水–甲基异丁基酮混合溶剂。