Department of Machine Intelligence and Systems Engineering Faculty of Systems Engineering, Akita Prefectural University , Akita 015-0055, Japan.
ACS Appl Mater Interfaces. 2017 Apr 19;9(15):13593-13601. doi: 10.1021/acsami.7b01003. Epub 2017 Apr 5.
The designed tough hydrogels, depending on energy dissipation mechanism, possess excellent biocompatibility, stimuli-responsiveness, and outstanding mechanical properties. However, the application of hydrogels is greatly limited in actuators and sensors for the lack of instantaneous recovery and resilience. In this work, we synthesized a double cross-linking poly(acrylic acid) hydrogel via a simple, one-pot, visible-light-trigger polymerization, with carboxymethyl cellulose as initiator and the first cross-linker, N,N'-methylene bis(acrylamide) (MBA) as the second cross-linker. The tensile strength and elastic modulus are in the range of 724-352 kPa and 115-307 kPa, respectively, depending on the MBA content. The swelling ratio of hydrogels dramatically decreased with increasing the MBA content. DMA results indicate that the internal friction between molecules within the hydrogel decreases with the increase of MBA content. Cyclic tensile tests show that after the structure stabilizes, the resilience, maximum stress, and residual strain of Gel-2 maintains over 93% (95% for successive cyclic tensile test), 115 kPa and less than 3%, respectively, at a strain of 125%. The values of resilience and residual strain are almost constant in both successive and intermittent cyclic tensile tests. Moreover, the swollen hydrogel has higher resilience and lower residual strain than the same hydrogel in the as-prepared state.
设计的坚韧水凝胶，根据能量耗散机制，具有优异的生物相容性、刺激响应性和出色的机械性能。然而，由于缺乏瞬时恢复和弹性，水凝胶的应用在驱动器和传感器中受到极大限制。在这项工作中，我们通过简单的一锅可见光引发聚合，以羧甲基纤维素作为引发剂和第一交联剂，N,N'-亚甲基双（丙烯酰胺）（MBA）作为第二交联剂，合成了一种双交联聚丙烯酸水凝胶。拉伸强度和弹性模量的范围分别为 724-352 kPa 和 115-307 kPa，这取决于 MBA 的含量。水凝胶的溶胀比随着 MBA 含量的增加而显著降低。DMA 结果表明，水凝胶内部分子之间的内摩擦力随着 MBA 含量的增加而降低。循环拉伸试验表明，在结构稳定后，在应变 125%时，Gel-2 的回弹性、最大应力和残余应变分别保持在 93%以上（连续循环拉伸试验为 95%）、115 kPa 以下和 3%以下。在连续和间歇循环拉伸试验中，回弹性和残余应变的值几乎保持不变。此外，与预制备状态下的相同水凝胶相比，溶胀水凝胶具有更高的回弹性和更低的残余应变。
