Multifunctional zwitterionic hydrogels: A review of cross-disciplinary applications

Owing to their unique molecular structure, zwitterionic hydrogels have emerged as a research hotspot in numerous fields in recent years. Cations and anions are uniformly distributed along the polymer chain. Consequently, zwitterionic hydrogels exhibit a large dipole moment and a high density of charged groups while effectively maintaining the overall electrical neutrality of the material. This charge balance not only endows the hydrogels with outstanding properties but also provides a valuable exploration space for breakthroughs in innovative application fields. This paper introduces the molecular structure and cross-linking mechanism of zwitterionic hydrogels, and analyzes the underlying reasons for their excellent hydration, favorable electrical conductivity, mechanical properties, environmental responsiveness and antifreeze performance. Additionally, it summarizes the significant applications of zwitterionic hydrogels in diverse fields such as sustainable water treatment, electrochemical devices, and biomedicine. Meanwhile, the current challenges faced by these materials, including large-scale production costs and high-salt swelling issues, are pointed out, so as to provide directions for future research.