Poly(sodium 4-styrenesulfonate) wrapped carbon nanotube with low percolation threshold in poly(ε-caprolactone) nanocomposites

Multi-walled carbon nanotubes (MWCNTs) were modified via a non-covalent functionalization technique with poly(sodium 4-styrenesulfonate) (PSS) as the modifier. A well dispersed and stable water dispersion of carbon nanotubes was prepared by ultrasonication of aqueous suspension of MWCNTs in the presence of PSS. Successful wrapping of MWCNTs by PSS was confirmed by High resolution transmission electron microscope (HRTEM). The dispersion was used to fabricate nanocomposites with poly(ε-caprolactone) (PCL) through solution coagulation. Scanning electron microscope (SEM) and transmission electron microscope (TEM) indicate that PSS wrapped MWCNTs dispersed uniformly in PCL matrix without obvious aggregation even with MWCNT loading increased up to 1.0 wt%. Rheological investigation confirmed that rheological network existed in the PCL/MWCNT nanocomposites with the percolation threshold of only 0.3 wt%. The electrical conductivity of the composites was investigated and the results indicate that electrical percolation threshold was also 0.3 wt%. The mechanical properties of PCL were significantly reinforced as evidenced by the improvement in yielding strength, Young's modulus, and dynamic storage modulus with incorporation of PSS wrapped MWCNTs.