Ultrastiff, Tough, and Healable Ionic–Hydrogen Bond Cross-Linked Hydrogels and Their Uses as Building Blocks To Construct Complex Hydrogel Structures

We report the ultrastiff and tough poly­(acrylamide-co-acrylic acid)/Na-alginate/Fe3+ (P­(AM-co-AA)/Na-alginate/Fe3+) hydrogel via the formation of hybrid ionic–hydrogen bond cross-linking networks. The optimal P­(AM-co-AA)/Na-alginate/Fe3+ hydrogel possessed super high elastic modulus (∼24.6 MPa), tensile strength (∼10.4 MPa), compression strength (∼44 MPa), and toughness (∼4800 J/m2). The P­(AM-co-AA)/Na-alginate/Fe3+ hydrogel was highly stable and maintained its superior mechanical properties in 0.5–2 M NaCl solution, aqueous solution with pH ranging from 4 to 10. The ionic cross-linking networks of the P­(AM-co-AA)/Na-alginate/Fe3+ hydrogels can be locally and selectively dissociated by treating with aqueous NaOH solution with pH of 13 for 1 min and reformed by locally adding the additional Fe3+ solutions, making the hydrogels healable and cohesive. The healed hydrogels from the cutting surfaces can bear a tensile strength of up to 7.1 MPa. Various complex hydrogel structures can be constructed by using the P­(AM-co-AA)/Na-alginate/Fe3+ hydrogels as building blocks via the adhesion of as-prepared hydrogels.本报告揭示了通过形成混合离子-氢键交联网络而制备的超高强度和韧性聚（丙烯酰胺-丙烯酸）/Na-藻酸盐/Fe3+（P(AM-co-AA)/Na-alginate/Fe3+）水凝胶。该最优化的P(AM-co-AA)/Na-alginate/Fe3+水凝胶展现出卓越的弹性模量（约24.6 MPa）、拉伸强度（约10.4 MPa）、压缩强度（约44 MPa）以及韧性（约4800 J/m2）。该水凝胶在0.5-2 M NaCl溶液以及pH值介于4至10的溶液中表现出极高的稳定性，并保持其优异的力学性能。P(AM-co-AA)/Na-alginate/Fe3+水凝胶的离子交联网络可通过用pH值为13的NaOH水溶液处理1分钟进行局部和选择性地解离，并通过局部添加额外的Fe3+溶液重新形成，从而使水凝胶具备自修复和粘合的特性。由切割表面修复后的水凝胶能够承受高达7.1 MPa的拉伸强度。利用P(AM-co-AA)/Na-alginate/Fe3+水凝胶作为构建模块，可以通过预先制备的水凝胶的粘附来构建各种复杂的凝胶结构。