Optimized Association of Short Alkyl Side Chains Enables Stiff, Self-Recoverable, and Durable Shape-Memory Hydrogel.

This work reports a self-healing and shape-memory hydrogel integrating multiple mechanical properties. The network configuration is featured as entangled networks cross-linked by distributed association of very short alkyl chains (hexyl, six carbons). These cross-linking knots are interconnected by the long hydrophilic polyvinyl alcohol backbone. The optimal aggregation of hexyl side chains leads to the broadened distribution in bonding strength as verified by static and dynamic mechanical characterization. These structural features contribute to high strength, toughness, stiffness, and yet fast recoverability. Furthermore, the hydrophobic and supramolecular nature of aggregated alkyl chains offers high durability and solvent-assistant healing function. Finally, distributed association of hexyl side chains confers a broadened temperature-dependent modulus, allowing for encoding stepwise shape recovery from a temporary shape at different temperatures and/or times.