Crystalline-Constrain Enables Preparation of Hierarchical Porous Hydrogels with High Porosity and Good Mechanics

Porous hydrogels with high porosity can achieve high matter diffusion and transport efficiency. Achieving both ultrahigh porosity and excellent mechanical properties in porous hydrogels remains a long-standing challenge, considerably hindering their use in high load-bearing elastic scaffolds such as artificial articular cartilages and meniscus replacements. Herein, a novel crystalline-constrained multi-solvents template preparation method is proposed for synthesizing highly porous hierarchical polyvinyl alcohol hydrogels (P-exogel) with excellent mechanical properties. The enhanced mechanical characteristics of the P-exogel are attributed to the crystallinity-induced network anti-swelling effect of the pore walls during dynamic template removal. The P-exogel exhibits a hierarchical and interconnected pore structure with high porosity (81.69%), resulting in ultrafast surface wetting with water (in less than 10 ms). Moreover, the P-exogel exhibits good tensile breaking strength (2.47 ± 0.53 MPa) with elongation of more than 400%, high toughness (5.61 ± 1.65 MJ m⁻³), and excellent elastic recovery performance. The pre-crack testing results further confirm the ultrahigh fracture resistance (18.73 ± 2.52 KJ m⁻²) of the P-exogel, which almost surpasses those of all reported and commercial porous hydrogels. The unique network microstructure of the P-exogel ensures its highly efficient and reversible liquid absorption and release ability during dynamic loading–unloading processes, confirming its great application potential in high load-bearing elastic scaffolds.