Ionic Conductive Elastomers Based on Soft and Hard Segment Crosslinked Copolymers

Flexible sensors can sense external stimuli and convert them into electrical signals that are easy to be analyzed statistically. They have enormous application potential in human motion detection, health monitoring, and human-machine interaction and other fields. It is important to develop flexible sensors with high ductility, transparency, conductivity and stability. Conductive elastomer is the key core material of flexible sensor. At present, transparent flexible sensors mainly use ionic conductive materials, including hydrogels, organic gels, ionic gels and ionic conductive elastomers. Ionic conductive elastomers are composed of ionic conductors and elastic polymer networks, which have conductive mechanism similar to skin, wide operating temperature range, high transparency and excellent reversible tensile-shrinkage performance, which are suitable to be used as transparent flexible sensors for human-machine interaction. In this work, the soft-hard crosslinked copolymer-based lithium ionic conductive elastomers were prepared via a one-step click polymerization reaction, and used as the flexible strain sensors for monitoring finger bending and Morse Code transmission information. The hard segment component consists of liquid crystal molecules, which tend to orderly arrange during the membrane stretching process, and enhance the mechanical properties of the elastomer. The soft segment is composed of polyethylene glycol dimethacrylate oligomer (M-n = 750 g/mol), which can not only increase the breaking elongation and transparency of ionic conductive elastomers, but also the ether oxygen segment contained can dissociate and transport lithium ions, and improve the conductivity of ionic conductive elastomers. By optimizing the proportion of components, ion conductive elastomers with different mechanical properties, transparencies, and conductivities can be obtained. The maximum elongation at break is 1280%, the maximum fracture stress is 5.08 MPa, the maximum modulus is 17.21 MPa, the transmittance is over 80%, and the maximum conductivity is 2.5 mS/ The ionic conductive elastomers with the best comprehensive properties possess high strain sensitivity with corresponding gauge factor values of 2.89, 4.61, and 5.39 in the strain range of 0. 200%, 200%-350%, and 350%-550%, respectively. This one-step soft-hard segment crosslinked copolymer strategy provides a new idea for preparing high-performance transparent ionic conductive elastomers.

Automated summary

In this study, a soft-hard segment crosslinked copolymer-based lithium ionic conductive elastomer was prepared via a one-step click polymerization reaction and used as a flexible strain sensor for monitoring finger bending and Morse Code transmission information. The elastomer exhibits high elongation, transparency, conductivity, and strain sensitivity.