Fully physically crosslinked supramolecular hydrogel with high tensile strength, low hysteresis, high adhesivity and frost resistance based on confinement effect

Abstract

Traditional ionic conductive hydrogel was prepared by chemically crosslinking the polymer chains to form network. However, the chemically crosslinked ionic conductive hydrogel usually showed limited elongation at break and high hysteresis during stretching process. Here, a simple strategy of synthesizing fully physically crosslinked ionic conductive supramolecular hydrogel without chemical crosslinker was purposed. Hydrophilic salt not only act as the ion supplier, but also provide the spatial confinement effect to form the completely physically crosslinked hydrogel. Firstly, CaCl₂ was used as the representative salt. The optimal PVA/PAM/CaCl₂ ionic conductive hydrogel (PPC), showed excellent tensile performance (2400.3 ± 140.63 %), anti-freezing performance (−28.8 °C), high conductivity (4.8 ± 0.01 S/m), excellent stability at room temperature, low hysteresis, and high transparency. The conductivity of PPC showed no sensitivity to the tensile strain. This innovative combination enables PPC ionic conductive hydrogel to have extraordinary versatility. The flexible all-solid-state supercapacitor assembled with PPC ionic conductive hydrogel as the electrolyte has a high area specific capacitance (136.9 mF/cm²). The prepared supercapacitor can maintain good stability under certain tensile deformation (The capacitance retention rate was 87.7 % when stretched at 200 %). Moreover, other high hydrophilic salts including LiCl, ZnCl₂, MgCl₂ and AlCl₃ were used to prepare ionic conductive PVA/PAM hydrogel to verify the universality of this preparation method.