Photo-crosslinkable comb-type copolymers bearing a benzophenone moiety for the enhanced swelling kinetics of hydrogels

Photo-polymerization has been intensively studied for the preparation of hydrogels because of several attractive features, including independent spatial control with photomasks, mild reaction conditions, and a simple procedure. Benzophenone (BP) and its derivatives are representative photoactive materials for the crosslinking of polymer chains; however, the incorporation of BP in a polymer chain results in low solubility in water, low swelling ratio, and slow swelling kinetics of the hydrogels. In this work, we have synthesized photo-crosslinkable copolymers of grafted PNIPAm and a benzophenone moiety. We could fabricate the hydrogels by UV illumination of the synthesized copolymers, and found that the fabricated hydrogels showed enhanced swelling kinetics through free chains of comb-type copolymers. We also demonstrated volume changes of the 3D hydrogel triggered by temperature, suggesting that the prepared copolymers can be applied to the fabrication of stimuli-responsive and fast responding origami patterns, actuators, and so on.