Visible light induced synthesis of high toughness, self-healing ionic hydrogel and its application in strain sensing

[Display omitted] •Ionic double crosslinked hydrogel synthesized by facile, visible-light-triggered polymerization and salt impregnation.•The hydrogel overcomes the limited recoverability of common hydrogels and shows excellent mechanical properties.•The hydrogel-based capacitance sensor showed a good linear correlation and quick response to strain in a wide range (0∼300 %). The conductive hydrogels with high recovery property applied in electronic sensor fields have recently attracted more and more attention. However, it remains a challenge to simply develop gel-based sensors with excellent toughness, recovery ability and stretch stability. In this work, a tough double crosslinked hydrogel (DC-Gel) was obtained from polyvinyl alcohol/poly (acrylic acid) (PVA/PAA) by facilely visible light triggered polymerization and subsequent salt impregnation. The ionic DC-Gels have been proofed with a high toughness (up to 19 MJ/m3), recovery property, self-healing ability and conductivity. The rubber-like flexible network and homogeneous interconnected phase of the ionic DC-Gels were certificated by scanning electron microscope and thermodynamics analysis. The tensile strengths and stretches at break of the ionic DC-Gels closely depended on the acrylic acid (AA) content. Cyclic tensile test results showed that the ionic DC-Gels with the optimized AA content (PVA:AA = 1:5) afforded a good comprehensive mechanical properties and recoverable energy dissipation; the resilience and stress of the hydrogel at a strain of 150 % maintained over 85 % and 1.8 MPa, respectively. When the ionic DC hydrogel was applied to assemble a strain sensor, the excellent resilience is beneficial for precisely and quickly distinguishing the deformation of hydrogel-based sensor. This research provides a potential approach for the development of ion hydrogels with stretchable, self-healing, high resilience and strain-sensitive properties.