As a promising class of tough and ultrastretchable hydrogels, micellecrosslinked hydrogels have been restrained by the scarcity of micellar crosslinkers with a high concentration, controlled nanostructure, and uniform size distribution. Herein, polymerization-induced self-assembly (PISA) was demonstrated to be a general and powerful platform for micellar crosslinkers, affording micelle-crosslinked hydrogels with tailorable chemical structures, mechanics, and functionality. Poly(N,N-dimethylacrylamide)-b-poly(diacetone acrylamide) (PDMAc-b-PDAAM) micellar crosslinkers with a controlled nanostructure and uniform size distribution were prepared via PISA and onestep post-polymerization modification at high concentrations. Copolymerization of these micellar crosslinkers with acrylamide generated tough and ultrastretchable hydrogels, whose mechanical properties were found correlated with the concentration, nanostructure, and chemical composition of the micelles. The energy dissipation mechanism of these micelle-crosslinked hydrogels was analyzed via cyclic mechanical tests and stress relaxation experiments. The general feasibility of PISA toward micelle-crosslinked hydrogels was verified by systematic evaluation of both aqueous (including 2-methoxyethyl acrylate, tetrahydro-2-furanylmethyl acrylate, and 4-hydroxybutyl acrylate) and alcoholic (including benzyl methacrylate, lauryl methacrylate, styrene, and benzyl acrylate) PISA formulations, producing hydrogels with diverse chemical structures, mechanics, and functionalities depending on the micellar crosslinkers. The modularity of this strategy was further demonstrated by the fabrication of fluoro-functionalized hydrogels with fluoro-containing micellar crosslinkers. This strategy has significantly enlarged the scope and application of micelle-crosslinked hydrogels.

In nature, the hierarchical structure of biological tissues endows them with outstanding mechanics and elaborated functions. However, it remains a great challenge to construct biomimetic hydrogels with well-defined nanostructures and good mechanical properties. Herein, polymerization-induced self-assembly (PISA) is for the first time exploited as a general strategy for nanostructured hydrogels and organogels with tailored nanodomains and outstanding mechanical properties. As a proof-of-concept, PISA of BAB triblock copolymer is used to fabricate hydrogels with precisely regulated spherical nanodomains. These nanostructured hydrogels are strong, tough, stretchable, and recoverable, with mechanical properties correlating to their nanostructure. The outstanding mechanical properties are ascribed to the unique network architecture, where the entanglements of the hydrophilic chains act as slip links that transmit the tension to the micellar crosslinkers, while the micellar crosslinkers dissipate the energy via reversible deformation and irreversible detachment of the constituting polymers. The general feasibility of the PISA strategy toward nanostructured gels is confirmed by the successful fabrication of nanostructured hydrogels, alcogels, poly(ethylene glycol) gels, and ionogels with various PISA formulations. This work has provided a general platform for the design and fabrication of biomimetic hydrogels and organogels with tailorable nanostructures and mechanics and will inspire the design of functional nanostructured gels.

Reaction-induced phase transition (RIPT) is an emerging strategy that allows the self-assembly of polymers and the regulation of nanoparticle morphology by in-situ chemical reactions. Despite the great potential, the driving...