Hydrogels are often limited in their applications due to their inherently weak mechanical properties. In this study, a carboxyl-functionalized hyperbranched polymer (HPEHO-star-PAA) was synthesized and used as a macromolecular physical cross-linker to enhance the mechanical properties of conductive hydrogels. Fe3+–carboxyl complexes were incorporated into the P(AAm-co-AA)/HPEHO-star-PAA hydrogel to form a dual cross-linked network structure. The cross-linker N,N′methylenebis(acrylamide) (MBA) was chemically incorporated into the network to form covalent cross-links, strengthening the network. Meanwhile, the coordination bonds formed between Fe3+ and carboxylate act as dynamic noncovalent cross-links, enhancing the energy dissipation capacity. This study successfully prepared a hydrogel with excellent mechanical properties, including an elongation at break of 573%, a tensile strength of 3.68 MPa, and a toughness of 14.09 MJ/m3. Additionlly, the conductive hydrogels also showed good antiswelling ability due to the strong binding force between Fe3+ and carboxylate. Moreover, P(AAm-co-AA) hydrogels used as strain sensors possessed stability and were highly sensitive. Therefore, this well-designed conductive hydrogel, with high mechanical strength, excellent toughness, good antiswelling ability, and high sensitivity, shows great potential for use in flexible strain sensor applications.
Zhang et al. (Fri,) studied this question.