Highly Stretchable and Reconfigurable Ionogels with Unprecedented Thermoplasticity and Ultrafast Self-Healability Enabled by Gradient-Responsive Networks

Abstract

Nonvolatile and durable ionogels are emerging and promising stretchable ionic conductors for wearable electronics. However, the construction of reconfigurable and recyclable ionogels with high mechanical robustness, high stretchability, and autonomous healability, while heavily demanded, is very challenging. Here, we present a gradient-responsive cross-linking strategy for preparing a highly stretchable and reconfigurable thermoplastic engineering ionogel (TPEI). The design of both microcrystalline and dense hydrogen bonds in TPEI contributed to the formation of a unique gradient-responsive network. When the TPEI was melt-processed under heating, the microcrystalline network structure was destroyed to form entangled polymer chains, while the high-density hydrogen-bonded network structure was only partially destroyed. The remaining hydrogen-bonded network allowed the TPEI to have a high viscosity for melt processing. When the TPEI was cooled upon melting injection, extrusion, and spinning, the hydrogen-bonded network was rapidly reconstructed in tens of seconds, allowing it to be reconfigured and reshaped, while the microcrystalline network was further reconstructed to improve its mechanical strength and elasticity during subsequent aging. As a result, the TPEI exhibited engineering-hydrogel-level mechanical robustness (>100 kPa), extremely high stretchability (>1000%), wide-temperature tolerance (−20 to 80 °C), and ultrafast self-healability in few seconds. Due to its mechanical adaptability, high ionic conductivity, and reconfigurability, the TPEI was demonstrated to readily work as a self-healable and recyclable stretchable conductor in a wearable skin-inspired sensor for monitoring sophisticated human motions.