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Abstract Hydrogels are often synthesized through photoinitiated step‐, chain‐, and mixed‐mode polymerizations, generating diverse network topologies and resultant material properties that depend on the underlying network connectivity. While many photocrosslinking reactions are available, few afford controllable connectivity of the hydrogel network. Herein, a versatile photochemical strategy is introduced for tuning the structure of poly(ethylene glycol) (PEG) hydrogels using macromolecular monomers functionalized with maleimide and styrene moieties. Hydrogels are prepared along a gradient of topologies by varying the ratio of step‐growth (maleimide dimerization) to chain‐growth (maleimide‐styrene alternating copolymerization) network‐forming reactions. The initial PEG content and final network physical properties (e.g., modulus, swelling, diffusivity) are tailored in an independent manner, highlighting configurable gel mechanics and reactivity. These photochemical reactions allow high‐fidelity photopatterning and 3D printing and are compatible with 2D and 3D cell culture. Ultimately, this photopolymer chemistry allows facile control over network connectivity to achieve adjustable material properties for broad applications. 

Liquid crystal elastomers leap via thermally induced snap-through transitions facilitated by spatial programming of properties. 

Abstract Diarylethene‐functionalized liquid‐crystalline elastomers (DAE‐LCEs) containing thiol‐anhydride bonds were prepared and shown to undergo reversible, reprogrammable photoinduced actuation. Upon exposure to UV light, a monodomain DAE‐LCE generated 5.5 % strain. This photogenerated strain was demonstrated to be optically reversible over five cycles of alternating UV/Visible light exposure with minimal photochrome fatigue. The incorporation of thiol‐anhydride dynamic bonds allowed for retention of actuated states. Further, re‐programming of the nematic director was achieved by heating above the temperature for bond exchange to occur (70 °C) yet below the nematic‐to‐isotropic transition temperature (100 °C) such that order was maintained between mesogens. The observed thermal stability of each of the diarylethene isomers of over 72 h allowed for decoupling of photo‐induced processes and polymer network effects, showing that both polymer relaxation and back‐isomerization of the diarylethene contributed to LCE relaxation over a period of 12 hours after actuation unless bond exchange occurred.