Dynamic Hydrophobic Domains Enable the Fabrication of Mechanically Robust and Highly Elastic Poly(vinyl alcohol)-Based Hydrogels with Excellent Self-Healing Ability

Abstract

It is a great challenge to fabricate self-healing hydrogels that simultaneously possess high mechanical strength and good elasticity, and are capable of rapidly and efficiently healing physical damage. In this work, such hydrogels are fabricated by grafting 4-carboxybenzaldehyde (CBA) onto poly(vinyl alcohol) (PVA) in dimethyl sulfoxide, followed by sequential dialysis in ethanol and water. The dialysis in ethanol generates hydrogen-bond-cross-linked PVA-CBA organogels with homogeneous structures while the subsequent dialysis in water leads to PVA-CBA hydrogels uniformly dispersed with hydrogen-bond-cross-linked hydrophobic domains. The in-situ-formed hydrophobic domains with an average diameter of ∼13 nm can strengthen the PVA-CBA hydrogels to a tensile strength of ∼5.8 MPa and toughness of ∼14.9 MJ m–3, and endow the hydrogels with good elasticity. Because of the presence of hydrogen bonds, the hydrophobic domains can reversibly break and reform to enable the rapid and efficient self-healing of fractured hydrogels at room temperature to restore their original mechanical strength. Meanwhile, the hydrogels have good biocompatibility and are potentially useful as post-operative antiadhesive films.