Mechanically Robust Lubricating Hydrogels Contrived by Harnessing Low-Entropy Nanocrystalline Polymer Network

Abstract

Hydrogels with extraordinary mechanics hold tremendous application prospects in the field of artificial human load-bearing tissues, but the invention of cartilage-like hydrogels with unprecedented mechanical robustness and dependable lubricity is still a substantial challenge. Herein, a low-entropy nanocrystalline domains network control strategy is proposed to construct mechanically robust poly (vinyl alcohol)/chitosan (PVA/CS) hydrogels with superior and durable lubrication performance. Consequently, the resulting PVA/CS hydrogels feature tunable mechanical performance by altering interaction between PVA and CS in the polymer network, spanning fracture strength, elastic modulus, toughness, and stretchability. Furthermore, its friction coefficient against the Al₂O₃ ball keeps as low as 0.034 for 1 × 10⁵ reciprocating cycles at 5 N, 1 Hz with water as the tribological medium, and even no destructive wear is found after friction test. To exploit the applications, PVA/CS hydrogels are processed into a femoral head and rubbed against swine acetabulum and found to have comparable lubricating properties to natural animal cartilage, positioning it as a superior competitor within the realm of durable lubricating hydrogel systems. This work corroborates the supposition that inducing polymer chains to form low-entropy nanocrystalline domain structures is able to yield robust hydrogels with extraordinarily enhanced mechanical performances.