Recyclable, healable, and stretchable thermoset shape memory polythiourethane/carbon nanotube composite with segregated conductive structure for strain sensing

Abstract

Segregated conductive polymer composites (CPCs) show high conductivity at low loading of filler. However, the weak interactions between fillers and polymer matrix may destroy the mechanical property of the segregated CPCs. Moreover, even with the introduction of dynamic bonds in thermoset polymers, the preparation of thermosetting CPCs remains a big challenge, as most crosslinked polymers should be ground into granules or crushed into powder with liquid nitrogen before mixing with fillers. Herein, the dynamic crosslinked polythiourethane microspheres (PTUM) are designed and synthesized. Then, a special mixing method (the mixing temperature is higher than melting temperature of soft segments of PTUM) is used to make the carbon nanotubes (CNTs) adhering closely to the surface of the crosslinked PTUM, promoting the formation of compacted conductive network. The CNT-3%/PTUM shows the electrical conductivity of 21.9 S/m and an elongation at break of 472%. Additionally, the CNT/PTUM composites exhibit good self-healing property, reprocessability, and close-loop recycling property. The construction of dynamic crosslinked microspheres and compacted segregated conductive network in this work supplies a new approach to prepare thermoset CPCs with simultaneous high electrical conductivity and mechanical property, which is expected to be applied to wearable strain sensors.