Supramolecular Poly(Ionic Liquid)-Based Humidity andDeformation-Insensitive Sensor for Ultrasensitive Temperature Sensing

Abstract

A variety of ionic liquid matter has been explored for superior temperature sensing with high-pressure resolution across a broad temperature range. However, it is not so wearable, since its performance is often compromised by environmental humidity or deformations. In this work, we present a linear poly(ionic liquid) elastomer via an in situ polymerization of the carefully selected hydrophobic ionic liquid monomer, tetra-n-butylphosphonium p-styrenesulfonate ([P₄₄₄₄][SS]), named as P-[P₄₄₄₄][SS]. P-[P₄₄₄₄][SS] exhibits remarkable thermosensitivity with a high sensitivity exceeding 8.1%/K and an exceptional resolution of 0.05 °C across an impressive range of −30 to 65 °C. The hydrophobic nature of the ions with assistance of the dense network ensures little water absorption even under 90% humidity condition, giving humidity-independent ionic conduction. The rigid π–π stacking in the polyanion and complex supramolecular cross-linkers within P-[P₄₄₄₄][SS] facilitates deformation energy dissipation, resulting in a deformation-insensitive temperature sensor. The temperature error is 0.3 °C under a deformation of 30%, indicating that the P-[P₄₄₄₄][SS] sensor is wearable with high reliability and adaptability. A wireless P-[P₄₄₄₄][SS]-based temperature sensor was fabricated to detect its wearable applications. These results underscore the importance of structure design for poly(ionic liquids), offering a promising avenue for future technological advancements.