Polymerization-Induced Self-Assembly Toward Micelle-Crosslinked Tough and Ultrastretchable Hydrogels

As a promising class of tough and ultrastretchable hydrogels, micelle-crosslinked 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 one-step 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.