Recent Advances in High-Strength Zwitterionic Polymer Hydrogels: From Zwitterionic Properties to Mechanical Reinforcement Strategies

Abstract Zwitterionic polymers are polymers containing a pair of oppositely charged groups in their repeating units, which facilitate the formation of a hydration layer on the surface through ionic solvation. This strong hydration results in the remarkable properties of zwitterionic polymer hydrogels, including antifouling, lubricating, and anti-freezing capabilities. Owing to these properties, zwitterionic polymer hydrogels have attracted notable attention in biomedical and engineering fields. However, the superhydrophilicity of zwitterionic polymer hydrogels renders them brittle and weak, considerably limiting their use in load-bearing applications. Thus, there is an urgent need to improve the mechanical properties of zwitterionic hydrogels. In this work, we systematically review mechanical enhancement strategies for zwitterionic polymer hydrogels. We cover strategies applicable to hybrid and pure high-strength zwitterionic polymer hydrogels. Additionally, we discuss the advantages and limitations of various strength enhancement strategies.