Cogelling

Cogelling, or co-gelation, refers to the formation of two or more gel networks within a single material system, typically through concurrent or sequential gelation processes that yield an interpenetrating or composite hydrogel.

In practice, cogelling can arise from orthogonal crosslinking chemistries, where one component forms a network via ionic or physical interactions while another forms a covalently crosslinked network, or from sequential diffusion- and reaction-driven gelation that links two polymers in one pot.

Because the networks can be tuned independently or cooperatively, cogelling offers control over mechanical strength, stiffness, porosity, and transport properties. Common examples involve alginate with gelatin or collagen, and gelatin methacrylate with photoinitiated crosslinking; other systems pair poly(vinyl alcohol) with borax or chitosan-based gels.

Cogelled hydrogels find use in tissue engineering as scaffolds with cell-friendly microenvironments, in drug delivery where diffusion can be modulated, and in wound dressings and soft robotic components that require adaptable mechanics.

Challenges include phase separation between networks, mismatched gelation times, potential cytotoxicity of crosslinkers, and difficulties achieving reproducible architectures. Research aims to balance interfacial compatibility, network interpenetration, and process scalability. Cogelling is closely related to interpenetrating network gels and composite hydrogels, and it remains an active area of study for designing multifunctional soft materials.