Tough, Transparent, and Slippery PVA Hydrogel Led by Syneresis

Slippery and transparent polyvinyl alcohol (PVA) hydrogels with mechanical robustness exhibit broad applications in artificial biological soft tissues, flexible wearable electronics, and implantable biomedical devices. Most of the current PVA hydrogels, however, are unable to integrate these features, which compromises its performance in biological and engineering applications. To achieve such purpose, herein, a novel tactic is proposed, salting-out-after-syneresis of PVA, to realize a mechanically robust and highly transparent slippery PVA hydrogel. The syneresis of PVA sol is first conducted to form highly dense and transparent PVA polymer networks, then the salting-out effect tunes the aggregation of the polymer chains to rapidly induce the phase separation and crystallization. The resultant hydrogels show the transparency up to 98% in the visible region, the tribological coefficient down to 0.0081, and the excellent mechanical properties with strength, modulus, and toughness of 26.72 ± 1.05, 6.66 ± 0.29 MPa, and 55.21 ± 1.62 MJ m^-3 , respectively. To reveal the potentials, PVA contact lens that combine remarkable lubrication, anti-protein adhesion, biocompatibility, and drug-loading functions are demonstrated. This strategy provides a simple and new avenue for developing the mechanically robust, transparent, and hydrated hydrogels, showing the potential in biomedicine and wearable devices.