Hydration Induces Dehydration: Creating Negative Swelling Gel by a Paradox

Abstract

Abstract Swelling positively in water is a common behavior of hydrogels, which, however, can lead to reduced mechanical performance and stability. Enabling negative swelling represents a promising way to address those issues but is extremely challenging to realize. Here, real negative swelling hydrogels are successfully prepared for the first time through a unique molecular architecture. Specifically designed interpenetrating transformable‐rigid polymer network undergoes self‐assembly and collapses upon hydration, which in turn dehydrates itself. This paradoxical hydration‐induced‐dehydration process brings about revolutionary outcomes. Gels can now lose up to 35% weight underwater and exhibit water‐strengthened mechanical properties, enhanced structural responsiveness, underwater repair ability, resistance to deformation, and swelling turn‐off effect. Those unique properties allow future material development and applications to be carried out in much broader dimensions.