Fabrication of self‐healable, conductive, and ultra‐strong hydrogel from polyvinyl alcohol and grape seed–extracted polymer

Abstract Developing hydrogels with excellent mechanical performances and multiple functions is challenging. Herein, polyvinyl alcohol (PVA) and grape seed extracted polymer (GSP) were used to achieve this goal. The hydrogel was firstly cross‐linked by crystalline regions of PVA upon freezing–thawing cycles, it was further immersed in ammonium sulfate (AS) solution to induce the hydrophilic to hydrophobic transition of GSP. The relationship between microstructures and mechanical properties of the obtained PVA–GSP hydrogel was revealed. The results showed that the PVA–GSP precursor hydrogels were weak due to the uneven network and lower cross‐link density. After soaking in ammonium sulfate solution, the network became more dense and uniform because of the hydrophilic to hydrophobic transition of GSP. Meanwhile, frictions between polymer chains increased. As a result, ultra‐strong (tensile stress = 20.5 MPa), antifatigue (>95%), self‐healable (healed stress = 10.0 MPa), and conductive hydrogels were obtained. The strength and toughness of our gel are among top values in literature to date. Furthermore, the swollen gel even after soaking in DI water for 36 hr still maintained tensile strength at the megapascal level, superior to most water‐rich hydrogels. This tough and functional gel might find potential applications in cartilage repair, artificial skin, and sensors.