Schiff base and coordinate bonds cross-linked chitosan-based eutectogels with ultrafast self-healing, self-adhesive, and anti-freezing capabilities for motion detection

Ion conductors offer great potential for diverse electric applications. However, most of the ion conductors were fabricated from non − degradable petroleum−based polymers with non or low biodegradability, which inevitably leads to resource depletion and waste accumulation. Fabricating ion conductors based on renewable, and sustainable materials is highly desirable and valuable. Herein, a series of eutectogels were designed through dual−dynamic−bond cross−linking among ferric iron (Fe3+), protocatechualdehyde (PA), and chitosan (CS) in 1 − allyl−3 − methylimidazole chloride ionic liquid/urea (AmimCl/urea) eutectic−based ionic liquid. Due to the presence of AmimCl/urea eutectic−based ionic liquid, the obtained CS − PA@Fe eutectogels showed excellent ionic conductivity, superior anti−freezing properties that could maintain flexibility and high electrical properties at −20 °C. Dual−dynamic−bond cross−linking of catechol−Fe coordinate and dynamic Schiff base bonds equip CS − PA@Fe eutectogels with excellent injectable, and self−healing abilities. Additionally, due to the presence of phenolic hydroxyl groups of PA, the obtained CS − PA@Fe eutectogels present good adhesiveness. Based on the CS − PA@Fe eutectogels, multifunctional flexible strain sensors with high sensitivity, stability, as well as rapid response speed at wide operating temperature ranges were successfully fabricated. Thus, this study offers a promising strategy for fabricating naturally occurring biopolymers based eutectogels, which show great potential as high−performance flexible strain sensors for next−generation wearable electronic devices.