Bottlebrush architecture enhanced π–π stacking drives supramolecular hydrogel assembly

We report supramolecular bottlebrush (sBB) hydrogels that assemble through unexpectedly strong π–π stacking between s-tetrazine groups tethered at the termini of densely grafted side chains. The networks form without covalent crosslinkers, remain stable up to ~65 °C, undergo reversible solid–liquid transitions under shear, and disassemble upon tetrazine deactivation. By contrast, linear polymers functionalized with tetrazine fail to form hydrogels, underscoring the essential role of bottlebrush architecture in promoting π–π stacking. By systematically varying tetrazine grafting density, we uncover a scaling relationship that unifies the concentration and functionality-dependent modulus of sBB hydrogels. Subcutaneous injection into immunocompetent mice reveals uniform cell infiltration and negligible fibrous encapsulation. Together, these findings identify bottlebrush-architecture-enhanced tetrazine–tetrazine stacking as a previously unrecognized supramolecular motif and establish sBB hydrogels as a versatile platform for engineering dynamic, tissue-mimetic materials.