Disulfide-Mediated Confinement Assembly Enabling Thermal-Hyperhardening Hydrogels via Phase Evolution.

Abstract

In a continuous material life cycle, driving multi-step, autonomous phase evolution-from physical assembly to chemical reconfiguration, and ultimately achieving a leapfrog improvement of macroscopic material properties represents a critical challenge in developing next-generation adaptive materials. Herein, we propose a dynamic covalent disulfide-mediated confinement assembly strategy, wherein thioctate is integrated into poly(acrylic acid) networks to demonstrate the biomimetic phase evolution process. The resultant polymer exhibits thermal-induced hyperhardening transition from a soft hydrogel to a rigid glassy material, with a record-breaking 27 000-fold increase in modulus, from 8 × 10^-4 to 22 MPa. The significant mechanical reinforcement is attributed to thermal-driven hydrophobic aggregation of 1,2-dithiolane motifs. The local concentrated monomers further trigger the disulfide-mediate ring-opening polymerization into covalently crosslinked microspheres, which effectively reinforce poly(acrylic acid) backbones via dynamic reconstruction of calcium (II) -carboxyl coordination. The potential application of soft actuators featuring composite architectures is demonstrated by integrating the rapid hyperhardening transition and prolonged mechanical stability of the hydrogels, as well as robust interfacial bonding capability via disulfide exchange. This universal phase evolution strategy based on dynamic covalent chemistry establishes an ideal material platform for developing multi-mode, on-demand regulation of high-performance adaptive materials.