Transient and directional growth of supramolecular hydrogels through reaction-diffusion-mediated self-assembly for dynamic wet gluing

The growth of supramolecular structures in biological systems is usually featured by dynamics and directionality, yet remains a real challenge in synthetic scenarios. Here, we show our access to transient and directional growth of supramolecular hydrogels through a simple reaction-diffusion-mediated self-assembly strategy. Transient and directional propagation of acid/base gradients are achieved through the diffusions of acid and base from opposite directions followed by the neutralization reaction at their crossing of diffusional fronts. The propagating distance maxima and lifetimes of the gradients can be easily controlled by changing the contents of acid/base. By coupling pH-sensitive gelators to the reaction-diffusion system, transient and directional growth of supramolecular hydrogels with controlled width maxima and lifetimes is realized. The growing direction of the hydrogel fibers at the microscopic level is demonstrated to be dominated by the gradient strengths of the pH signals and gelators. We further leverage the dynamic and directional gelation at the wet interface of soft hydrogel substrates for a proof-of-concept application of dynamic wet gluing.