Conductive epoxidized natural rubber/chitin nanocrystals/polyaniline composite with high toughness, high strength, and low hysteresis for flexible strain sensors

Abstract

Low hysteresis and mechanical toughness are important to improve the accuracy and timeframe of use of flexible sensors. However, constructing conductive flexible sensors with high mechanical strength, low hysteresis, and high toughness simultaneously remains a challenge. In this work, we construct an entangled crosslinked topological network with physical interactions to fabricate conductive flexible sensors with high mechanical strength and toughness, and low hysteresis. Pre-deacetylated chitin nanocrystals (ChNCs) were grafted onto epoxidized natural rubber (ENR), and then PANI was polymerized in situ. ChNCs with amino groups serve as templates for ANI polymerisation and provide junctions in the crosslinked network, enhancing molecular chain entanglement and crosslinking density. Upon loading, molecular chain conformations spontaneously adjust to equilibrium. Meanwhile, hydrogen bonding and electrostatic interactions with low strength exist between the polymer matrix and conductive fibres, which could rapidly break and reform during cyclic deformation. Therefore, the synergistic interactions of the topological network and physical interactions endow the material with high mechanical performance (2.5 MPa, 1000%), a low energy dissipation ratio (13.6% at 300% cyclic strain) and low hysteresis (13.3% at 300% cyclic strain). This work shows an effective method to prepare conductive flexible sensors with high toughness, high strength and low hysteresis for human body signal detection. The sensors show good electrical responses to external stress and can be used to monitor the movement of human joints. This work develops an effective strategy for developing tough conductive sensors exhibiting low hysteresis, high toughness, and high strength, indicating their potential in healthcare technologies.