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Temperature-Responsive Supramolecular Hydrogels by Ternary Complex Formation with Subsequent Photo-Cross-linking to Alter Network Dynamics

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journal contribution
posted on 25.11.2019, 20:36 by Lei Zou, Bo Su, Christopher J. Addonizio, Irawan Pramudya, Matthew J. Webber
Supramolecular hydrogels prepared from host–guest physical cross-linking of polymers have versatile utility in a number of applications. Routes to integrate stimuli-responsive features in these materials are intended to add another dimension to enhance their functionality. Herein, a guest which forms a homoternary complex with the cucurbit[8]­uril macrocycle was appended to the ends of Pluronic F-127 polymers. This polymer undergoes temperature-responsive micelle formation, upon which CB[8] promotes their physical cross-linking via its host–guest interactions with the appended guests yielding a percolated hydrogel network. The particular guests used to form the homoternary complex can further be photo-dimerized to replace the physical host–guest interaction with a covalently bonded interaction. This change results in a reduction in hydrogel dynamics of roughly 2 orders of magnitude, yet temperature-responsive gelation and overall network architecture remain apparently unchanged. Hydrogels composed of micelles cross-linked by both supramolecular and photo-dimerized interactions support the injection and encapsulation of cells and enable inclusion and release of macromolecular payloads in vitro and in vivo. Thus, this approach points to a strategy to integrate external stimuli into supramolecular hydrogels through a combination of responsive polymers and light-directed supramolecular motifs.