Weakly Polar Poor Solvent Inducing Unique Microstructures in Crystalline Hydrogels

Despite its widespread application in modulating the properties of crystalline hydrogels, the solvent exchange process lacks a detailed mechanistic understanding of the associated structural evolution. To address this deficiency, we present a systematic study employing four distinct good-poor solvent systems. This investigation elucidates the structural evolution of poly(vinyl alcohol) hydrogels and quantifies a power-law relationship linking their mechanical performance to key microstructural characteristics. It is demonstrated that the synergistic interplay between weakly polar 1,4-dioxane and the highly soluble N-methylpyrrolidone drives the self-assembly of a highly ordered, “fish scale”-like microstructure. The resultant architecture, characterized by densely packed, oriented “arrowhead” lamellae, is responsible for the hydrogel’s exceptional mechanical robustness. Therefore, solvent exchange is redefined as a versatile methodology for the precise engineering of highly ordered, periodic microstructures with morphologies that can be finely controlled, providing a foundational platform for the rational design and enhancement of high-performance crystalline hydrogels.