Concentrated solutions of multi-walled carbon nanotubes modified with long-alkyl chains (eMWNTs) in a poly(vinyl chloride) (PVC)/cyclohexanone (CH) system are prepared. A cooperative effect between the eMWNTs, PVC and CH via van der Waals interactions, hydrogen bonding and halogen bonding is responsible for the improved solubility. After precipitation, the PVC/eMWNT nanocomposites are soluble in tetrahydrofuran (THF) at reasonably good concentration, meeting conditions required for the preparation of MWNT-based binder-free inks. The Young's modulus as well as thermal stability and conductivity of the nanocomposites are significantly improved compared with those of the parent PVC. Finally, when this PVC/eMWNT binary system is used as a filler for pure PVC a striking increase in the elongation at break (208%) for the resulting ternary PVC/eMWNTs/PVC system is observed.