Structural-Based Design of Hydrogels from Bilayer to Double-Network Structure

Bilayer hydrogels and double-network hydrogels represent two distinct categories of soft-wet materials, each characterized by unique network structures, design principles, synthesis methods, and primary functionalities. From a structure-function perspective, bilayer hydrogels consist of two distinct layers connected by an interface, utilizing stimuli-responsive materials for spatiotemporal actuations in response to external stimuli. In contrast, double-network hydrogels involve two interpenetrating yet independent networks, significantly enhancing mechanical properties by an order of magnitude (ranging from 10 to 100) compared to single-network hydrogels. In this talk, we will propose different design-synthesis strategies for preparing these two different types of hydrogels. Bilayer hydrogels are typically created through layer-by-layer polymerizations, integrating multiple cross-linked networks and stimuli-responsive polymers into the two immiscible phases, with careful consideration of interfacial compatibility. Conversely, the design of double-network hydrogels employs multiple-step polymerizations to integrate a brittle network and an elastic network, emphasizing the independence of these networks without the formation of chemical bonds or crosslinkers between them.