Key Strategies to Improve the Mechanical Strength and Toughness of Hydrogels: A Review

Strong and tough hydrogels (STHs) are widely used in various applications. However, their widespread adoption is often limited by inherent weaknesses in their mechanical strength and toughness. The development of STHs mainly depends on the introduction of diverse interactions and optimizing the polymer network structure. This review aims to compile detailed information on hydrogel reinforcement and toughening strategies, influencing factors, and evaluation methods and provides valuable references and guidance for compositional design, mechanical behavior control, and the application of STHs in civil engineering. First, this paper reviews key strategies to enhance the strength and toughness of hydrogels and elaborates in detail the working mechanism, advantages, drawbacks, and principal applications of each reinforcement strategy. Second, the influence of critical factors─such as monomer chemistry, nanofiller characteristics, water content─on mechanical performance is comprehensively examined. Third, it reviews the methods used for evaluating the strength and toughness of hydrogels and proposes a roadmap for developing a multiscale toughness assessment framework. Finally, this review assesses the potential applications of hydrogels in civil engineering, identifies key challenges, and outlines pathways for their resolution.