Visualization and Photo-Programming of Chain Entanglements in Hydrogel Networks by Disulfide Exchange

Polymer chain entanglement represents a fundamental topological constraint that dictates the physicochemical properties of hydrogels, yet spatially regulating and directly probing these constraints remain significant challenges. Here, we report a strategy for encoding and visualizing entanglement states within a lamellar hydrogel framework through the introduction of photo-responsive disulfide bonds. Controlled dehydration induces temporary topological constraints, which are subsequently fixed through topological rearrangement via UV-triggered disulfide exchange. Upon reswelling to equilibrium, these preserved states manifest as variations in lamellar spacing and corresponding color shifts. Using photomask patterning, the spatial distribution of the topological states can be mapped in two dimensions, and pH stimulation converts the patterned regions into three-dimensional shape morphing. These results establish a direct link between microscopic topological constraints and macroscopic optical/mechanical responses, providing a platform for hydrogels with spatially defined anisotropy and an interpretable topological readout.