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Abstract Co-continuous morphology in polymer blends has been well demonstrated to reduce percolation threshold and enhance electrical conductivity by selective dispersion of carbon nanotubes in one phase or at interfaces. In this work, a flexible, co-continuous, and conductive poly(ethylene-co-1-octene)/thermoplastic polyurethane/multi-walled carbon nanotube (POE/TPU/MWCNT) composite has been fabricated by controlling the dispersion of MWCNTs in the TPU phase. The interfacial interaction between the two polymers in the composites has been enhanced by using a gentle crosslinking reaction. The percolation threshold of the composites decreased from 0.43 to 0.29 vol% and electrical conductivity rose more than one order of magnitude after gentle crosslinking because of the very continuous TPU/MWCNT phase, the MWCNT fillers selective distribution, and the strong interfacial interaction between the two polymers. Furthermore, the complex viscosity, storage modulus, tensile strength, and elongation at break of the composites were improved by the gentle crosslinking reaction. For example, the composites with 0.58 vol% MWCNT fillers achieved 1.4- and 2.4-fold improvement in tensile strength and elongation at break after gentle crosslinking, respectively. In addition, the flexibility of the composites was well maintained by the gentle crosslinking reaction, resulting in excellent piezoresistive behavior of the composites. The stability and reliability of the piezoresistive response of the composites were enhanced by the gentle crosslinking reaction, owing to the stability of the MWCNT conductive network and the strong interfacial interaction. We propose that a gentle chemical crosslinking reaction between the two polymers is an alternative method for improving electrical conductivity and stabilizing the conductive network for co-continuous conductive polymer composites. Highlights • The interfacial interaction between TPU and POE was enhanced by a gentle crosslinking reaction. • The very continuous TPU/MWCNT phase was found in the crosslinking POE/TPU/MWCNT composites. • The crosslinking composites exhibited high electrical conductivity and low percolation threshold. • The stability and reliability of piezoresistive response were enhanced by the gentle crosslinking reaction. • The gentle crosslinking reaction also enhanced the mechanical properties of the composites. [ABSTRACT FROM AUTHOR]

Multi-walled carbon nanotubes (MWCNTs) are known for improving the mechanical and electrical properties of polymers. The dispersion state of MWCNTs in the polymer matrix is critical for the fabrication of high-performance nanocomposites. Here, we show a simple strategy for tuning the dispersion state of MWCNTs in poly(ε-caprolactone) (PCL) via graphene oxide (GO) nanosheets and to further balance electrical and mechanical properties of the PCL/MWCNT nanocomposites. The strong π-π interactions between MWCNTs and GO nanosheets lead to easy adsorption of MWCNTs on GO nanosheet surfaces to form GO/MWCNT hybrids that retard the aggregation of MWCNTs in PCL. Furthermore, the GO/MWCNT ratio could also affect the dispersion of GO/MWCNT hybrids in PCL. Three different dispersion states of MWCNTs were found in the PCL matrix, i.e. PCL/MWCNT, PCL/GO/MWCNT (1/4) and PCL/GO/MWCNT (2/1) nanocomposites that represented severe, low and almost no aggregation of MWCNTs, respectively. The GO/MWCNT hybrids with a 2/1 ratio showed better dispersion in PCL matrix than the hybrids with a 1/4 ratio and pristine MWCNTs. The PCL/GO/MWCNT nanocomposites with almost no aggregation of GO/MWCNT (2/1) hybrids exhibited the highest tensile strength and elongation at break in comparison to the PCL/GO/MWCNT (1/4) nanocomposites and PCL/MWCNT nanocomposites. However, the best electrical conductivity was achieved in the PCL/GO/MWCNT (1/4) nanocomposites due to the low aggregation of MWCNTs. [ABSTRACT FROM AUTHOR]