Abstract Different series of strong polyelectrolyte poly(N-isopropylacrylamide-co-sodium acrylate) P(NIPA-co-NaA) hydrogels and cryogels were prepared in aqueous solution. With changing the ionic comonomer NaA ratio in reaction mixture, the resulting physico-chemical and swelling properties varied significantly. The findings elucidated that ionic P(NIPA-co-NaA) gels exhibited multi-stimuli performances with pH-, temperature-, solvent-, surfactant- and salt-responsivity, showing more sensitivity than non-ionic PNIPA. Their swollen/collapsed behaviors were strongly dependent on various synthesis/external parameters, including the content of ionic comonomer, temperature and solvent polarity. The effects produced by non-solvents were qualitatively compared considering the aspects related to co-nonsolvency phenomenon and re-entrant swelling transition on the basis of weakening of PNIPA-water interactions. Measurements of the elastic properties and swelling degree of samples having different NaA content were treated by combining Flory-Rehner theory and rubber elasticity to interpret the experimental observations. The polymer-solvent interaction parameter χ of hydrogels was calculated from the swelling studies in water at different temperatures and was related to the composition and temperature. The ionic strength-reversibility and on-off switching kinetics of hydrogels and cryogels were studied in 10−5 M and 1.0 M of NaBr solutions. Diffusion kinetics showed that the swelling of ionic hydrogels is of non-Fickian-type transportation, however, non-ionic PNIPA hydrogels and P(NIPA-co-NaA) cryogels showed pseudo-Fickian diffusion. The resulting hydrogels and cryogels containing both temperature and pH-sensitive units are able to interact with oppositely charged groups via hydrophobic and electrostatic interactions.

中文翻译：

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具有强离解基团的高电荷热响应水凝胶和冷冻凝胶的 pH 敏感性和溶剂极性的多方面研究：物理化学性质的比较评估

摘要 在水溶液中制备了不同系列的强聚电解质聚(N-异丙基丙烯酰胺-共-丙烯酸钠)P(NIPA-co-NaA)水凝胶和冷冻凝胶。随着反应混合物中离子共聚单体 NaA 比例的改变，所得到的物理化学和溶胀性质发生了显着变化。研究结果表明，离子 P(NIPA-co-NaA) 凝胶表现出多种刺激性能，包括 pH、温度、溶剂、表面活性剂和盐响应性，比非离子 PNIPA 显示出更高的敏感性。它们的膨胀/塌陷行为强烈依赖于各种合成/外部参数，包括离子共聚单体的含量、温度和溶剂极性。在PNIPA-水相互作用减弱的基础上，考虑与共非溶解现象和重入溶胀转变相关的方面，定性地比较了非溶剂产生的影响。通过结合 Flory-Rehner 理论和橡胶弹性来解释实验观察结果，对具有不同 NaA 含量的样品的弹性性能和溶胀度的测量进行了处理。水凝胶的聚合物-溶剂相互作用参数 χ 是根据不同温度下在水中的溶胀研究计算得出的，并且与组成和温度有关。在 10-5 M 和 1.0 M 的 NaBr 溶液中研究了水凝胶和冷冻凝胶的离子强度可逆性和开关动力学。扩散动力学表明离子水凝胶的溶胀是非 Fickian 型输运，然而，非离子 PNIPA 水凝胶和 P(NIPA-co-NaA) 冷冻凝胶显示出伪 Fickian 扩散。由此产生的含有温度和 pH 敏感单元的水凝胶和冷冻凝胶能够通过疏水和静电相互作用与带相反电荷的基团相互作用。