Copolymer composition tailored carbon nanotube network breakdown and piezoresistivity of ethylene-vinyl acetate electroconductive composites

Herein, the development of carbon nanotube-based electromechanical sensors with excellent sensing range and gauge factor is reported. Electroconductive composites (EPCs) of ethylene–vinyl acetate random copolymer (EVAc) with different ethylene (E) and vinyl acetate (VAc) segment ratios and different volume fractions of carbon nanotube (CNT) were prepared. The E/VAc ratio was found to significantly impact the AC impedance, electron tunneling, CNT-CNT structural breakdown, effective aspect ratio, and electromechanical behavior. The percolation threshold of CNT was lowest in EPCs with VAc 12%; interestingly, though, the effective aspect ratio, as determined from the micromechanical modeling, was considerably increased in EPC with VAc 40%. With an increase in VAc content, the electrical conductivity decreased; however, the electromechanical response improved significantly. Crystalline content, interfacial wetting, critical strain for the shear strain-induced structural breakdown of percolated CNT network, and effective aspect ratio were found to correlate with the superior electromechanics of EVAc/CNT EPC.