State Key Laboratory of Bio-Fibers and Eco-Textiles, Collaborative Innovation Center for Marine Biomass Fibers, Materials and Textiles of Shandong Province, Institute of Marine Biobased Materials, College of Materials Science and Engineering, Qingdao University, Qingdao 266071, China.
College of Textiles and Clothing, Research Center for Intelligent and Wearable Technology, Intelligent Wearable Engineering Research Center of Qingdao, Qingdao University, Qingdao 266071, China.
ACS Appl Mater Interfaces. 2021 Jun 2;13(21):25383-25391. doi: 10.1021/acsami.1c04577. Epub 2021 May 20.
High water content usually contradicts the mechanics for hydrogels, and achieving both characteristics is extremely challenging. Herein, a novel confined-chain-aggregation (CCA) strategy is developed to fabricate ultrastrong and tough hydrogels without sacrificing their inherent water capacity. Based on the popular polyacrylamide/alginate (PAAm/Alg) system with a double network (DN), a poor solvent exchange is induced once PAAm is fully cross-linked but prior to ionic cross-linking of alginate. In this case, the alginate chains are restricted by the chemical PAAm network and undergo a confined-chain aggregation, which guarantees an interpenetrating network of both polymers and simultaneously generates micron-scale aggregates. In addition, after the subsequent water uptake, the accompanying formation of hydrogen bonds and metal-ligand coordination stabilizes the newly formed alginate aggregates, serving as large-scale cross-linking zones. However, the PAAm chains are anchored by the preformed cross-linking points and convert back to the uniformly distributed, high-water-content state, achieving a selected phase separation in a DN system. The combined CCA and hybrid cation cross-linking method gives mechanical strength and toughness to the PAAm/Alg hydrogels to reach approximately 30 and 5 times the traditional methods, respectively. This investigation provides a general strategy for the development of a new generation of double-network hydrogels, which will expand their application as structural materials for cartilage and soft robotics.
高含水量通常与水凝胶的力学性能相矛盾，而同时实现这两个特性极具挑战性。在此，提出了一种新颖的受限链聚集（CCA）策略，用于制备高强度、高韧性的水凝胶，同时保持其固有水容量。基于广受欢迎的聚丙烯酰胺/海藻酸钠（PAAm/Alg）双网络（DN）体系，一旦 PAAm 完全交联但藻酸盐的离子交联之前，就会导致不良的溶剂交换。在这种情况下，藻酸盐链受到化学交联的 PAAm 网络的限制，并经历受限链聚集，从而保证两种聚合物的互穿网络，同时生成微米级别的聚集物。此外，在随后的吸水后，氢键和金属配体配位的形成稳定了新形成的藻酸盐聚集物，充当大的交联区域。然而，PAAm 链被预形成的交联点锚定，并转换回均匀分布的高含水量状态，在 DN 体系中实现选择相分离。CCA 和混合阳离子交联方法的结合赋予了 PAAm/Alg 水凝胶机械强度和韧性，分别达到传统方法的约 30 倍和 5 倍。这项研究为新一代双网络水凝胶的发展提供了一种通用策略，将扩大它们作为软骨和软机器人结构材料的应用。
