Polyampholyte hydrogels are synthesized by one‐step copolymerization of cationic monomer 3‐(methacryloylamino)propyltrimethylammonium chloride, anionic monomers sodium p‐styrenesulfonate (NaSS), and methacrylic acid (MAA) without chemical crosslinker and adding salts. The hydrogels exhibit pH responsive shape memory behavior; the temporary shape of the hydrogel is formed manually after immersing in NaOH solution and fixed in HCl solution, while the shape recovery occurs by immersing in NaOH again. Most interestingly, the hydrogel shows a spontaneous shape change after the first shape memory cycle. When the recovered hydrogel with a little residual deformation is immersed in HCl again, it twists spontaneously and rapidly to the previous temporary shape. The spontaneous twisting and recovering can be repeated for ten times. Furthermore, the hydrogel swells quickly and is strengthened in HCl, while shrinks and weakens in NaOH during the shape change procedure. This unique synergistic effect of fast swelling, residual helical deformation, and increased strength plays a significant role in the spontaneous shape alternation. This new finding will initiate a new prosperous design for new soft actuators requiring successive actions.

中文翻译：

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具有pH调节形状记忆和自发驱动力的两性水凝胶

聚两性电解质水凝胶是通过阳离子单体3-（甲基丙烯酰氨基）丙基三甲基氯化铵与阴离子单体钠p的一步共聚而合成的-不含化学交联剂并添加盐的苯乙烯磺酸盐（NaSS）和甲基丙烯酸（MAA）。水凝胶表现出pH响应的形状记忆行为。水凝胶的临时形状是在将其浸入NaOH溶液中并固定在HCl溶液中后手动形成的，而形状恢复是通过再次浸入NaOH进行的。最有趣的是，在第一个形状记忆周期后，水凝胶显示出自发的形状变化。当将回收的具有少量残余变形的水凝胶再次浸入HCl中时，它会自发且迅速扭曲为先前的临时形状。自发的扭曲和恢复可以重复十次。此外，在变形过程中，水凝胶迅速膨胀并在HCl中增强，而在NaOH中收缩和减弱。快速溶胀的这种独特的协同作用，残余的螺旋形变形和强度的增加在自发形状交替中起着重要作用。这一新发现将为需要连续动作的新型软执行器启动新的繁荣设计。