Department of Materials and Production, Aalborg University, Fibigerstraede 16, 9220 Aalborg, Denmark.
Molecules. 2022 Aug 14;27(16):5177. doi: 10.3390/molecules27165177.
The equilibrium degree of swelling of thermo-responsive (TR) gels is strongly affected by the presence of ions in an aqueous solution. This phenomenon plays an important role in (i) the synthesis of multi-stimuli-responsive gels for soft robotics, where extraordinary strength and toughness are reached by soaking of a gel in solutions of multivalent ions, and (ii) the preparation of hybrid gels with interpenetrating networks formed by covalently cross-linked synthetic chains and ionically cross-linked biopolymer chains. A model is developed for equilibrium swelling of a TR gel in aqueous solutions of salts at various temperatures below and above the critical temperature at which collapse of the gel occurs. An advantage of the model is that it involves a a small (compared with conventional relations) number of material constants and allows the critical temperature to be determined explicitly. Its ability (i) to describe equilibrium swelling diagrams on poly(-isopropylacrylamide) gels in aqueous solutions of mono- and multivalent salts and (ii) to predict the influence of volume fraction of salt on the critical temperature is confirmed by comparison of observations with results of numerical simulation.
热响应 (TR) 凝胶的平衡溶胀度强烈受到水溶液中离子存在的影响。这种现象在以下两个方面发挥着重要作用：(i) 用于软机器人的多刺激响应凝胶的合成，通过将凝胶浸泡在多价离子溶液中，可以获得非凡的强度和韧性；(ii) 通过共价交联的合成链和离子交联的生物聚合物链形成互穿网络的混合凝胶的制备。本文针对低于和高于凝胶坍塌临界温度下 TR 凝胶在盐水溶液中的平衡溶胀现象，建立了一个模型。该模型的优点是它涉及的材料常数数量较少（与传统关系相比），并且可以明确确定临界温度。通过将观察结果与数值模拟结果进行比较，验证了该模型的能力：(i) 描述聚（异丙基丙烯酰胺）凝胶在单盐和多价盐水溶液中的平衡溶胀图；(ii) 预测盐的体积分数对临界温度的影响。
