A state-of-the-art review of multi-cross-linked hydrophobic associated hydrogels for soft electronic, biomedical, and environmental applications.

Thanks to their considerable toughness, self-recoverability, high swelling degree and stimuli-responsiveness, hydrophobic association (HA) hydrogels are promising in wearable electronics, biomedical applications and the water treatment industry. Multiple (physical and/or chemical) cross-links can also promote the above-mentioned properties, broadening the applications of the gels. Previous reviews on the HA hydrogels focused only on their mechanical and self-healing properties for biomedical applications. Herein, we aim to introduce HA hydrogels having multiple crosslinks (multi-cross-linked HA (MCHA) gels), discuss their various properties, and then present their (potential) practical applications. To explain, this review first describes the synthesis of MCHA gels. Then, the mechanical, rheological, self-healing, injectability, swelling, and stimuli-responsive properties of MCHA hydrogels are discussed. In the meantime, we suggest useful approaches to address the current challenges for the sake of improving these properties. Finally, based on the properties of MCHA gels, we introduce their (potential) applications in the fields of soft electronics, biomedicine, the environment, and superabsorbents, followed by evaluation of the performance of the developed devices in some cases. Taken together, this review can provide helpful perspectives for developing high-performance MCHA hydrogels.