Integration of hydrogen bonding interaction and Schiff-base chemistry toward self-healing, anti-freezing, and conductive elastomer

It is highly desirable to fabricate the elastomer integrating excellent mechanical property, self-healing, anti-freezing and conductive capability by green and efficient preparation process although it remains challenging. Herein, we prepared a class of self-healing, anti-freezing and conductive elastomers based on polymerizable deep eutectic solvents (PDES) via a combination of the multiple hydrogen bonding interactions and Schiff-base chemistry. Firstly, the PDES mixture derived from choline chloride (ChCl), acrylic acid (AA) and vanillin derived monomer (VAM) was synthesized. Then, the mixture of carboxymethyl chitosan (CMCS) and PDES was cured under UV light to fabricate the elastomer with dynamic dual-crosslinked network. In this case, the CMCS acting as physical and chemical dual-crosslinker formed a physical crosslinked network by multiple hydrogen bonds between the hydroxyl and carboxyl of PDES and CMCS, while a chemical crosslinked network generated by Schiff-base chemistry between the amino of CMCS and aldehyde of VAM. It was found that the conductivity of the elastomer was 0.3-1.14 mS/cm. The formation of the dynamic dual-crosslinked network not only significantly improved the mechanical properties of elastomers, but also endowed these elastomers with excellent self-healing capability with 92.1% self-healing efficiency after healing of 50 h. Specially, these elastomers exhibited excellent anti-freezing properties, and maintained flexibility at -50 degrees C. In addition, the applications of these conductive elastomers as strain sensor and wearable device to monitor human activities were also investigated, and the sensing capability of the elastomers was maintained even at -25 degrees C or after the self-healing process.