Graphene oxide-assisted dispersion of multi-walled carbon nanotubes in biodegradable Poly(ε-caprolactone) for mechanical and electrically conductive enhancement

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.