Poly(acrylamide-co-acrylic acid) hydrogels are synthesized by free-radical polymerization in a microwave oven, in a one-step procedure that provides reduction in time, energy and resources in comparison with conventional heating in aqueous solution. Hydrogel microstructures are analysed by scanning electron microscopy (SEM). Dynamic swelling tests are carried out at three pH values (3.0, 10.0 and 7.0) and two temperatures (25 and 37 °C) considering the conditions for hydrogel application. SEM pictures indicate irregular cellular and porous structure of microwave synthesized hydrogels, obtained as a result of simultaneous polymerization and water evaporation. The results of swelling measurements show that the swelling ratio at pH 7.0 and 10.0 increases with increasing in acrylic acid amount, while at pH 3.0 decreases. Swelling rate is higher at physiological temperature, and solvent diffusion is relaxation-controlled. Swelling of hydrogels follows the second-order kinetics. Rheological behaviour of hydrogels has been assessed using the results of frequency and amplitude sweep tests applied at the systems in equilibrium swollen state. Obtained data reveal a dominant elastic character and a long linear viscoelastic region (up to 2000 Pa), as well as a similar three-dimensional internal structure of investigated hydrogels. Graphical abstract

中文翻译：

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微波合成聚（丙烯酰胺-共聚-丙烯酸）水凝胶的溶胀动力学和流变行为

聚（丙烯酰胺-共聚-丙烯酸）水凝胶是通过在微波炉中自由基聚合合成的，与传统的水溶液加热相比，一步法可减少时间、能源和资源。通过扫描电子显微镜 (SEM) 分析水凝胶微结构。考虑到水凝胶应用的条件，在三个 pH 值（3.0、10.0 和 7.0）和两个温度（25 和 37 °C）下进行动态溶胀测试。SEM 图片表明微波合成水凝胶的不规则蜂窝状和多孔结构，是通过同时聚合和水蒸发获得的。溶胀测量结果表明，在 pH 7.0 和 10.0 时，溶胀比随着丙烯酸用量的增加而增加，而在 pH 3.0 时则降低。在生理温度下溶胀率较高，溶剂扩散受松弛控制。水凝胶的溶胀遵循二级动力学。水凝胶的流变行为已使用在平衡膨胀状态下的系统中应用的频率和幅度扫描测试的结果进行评估。获得的数据揭示了主要的弹性特征和长的线性粘弹性区域（高达 2000 Pa），以及所研究的水凝胶的类似三维内部结构。图形概要 获得的数据揭示了主要的弹性特征和长的线性粘弹性区域（高达 2000 Pa），以及所研究的水凝胶的类似三维内部结构。图形概要 获得的数据揭示了主要的弹性特征和长的线性粘弹性区域（高达 2000 Pa），以及所研究的水凝胶的类似三维内部结构。图形概要