Novel Dispersion of MWCNTs in Polystyrene Polymer Induced by the Addition of 3-Hydroxy-2-Napthoic Acid

This article reports an extensive investigation of the unique dispersion behavior of solutions with multi-walled carbon nanotubes (MWCNTs) and 3-hydroxy-2-napthoic acid (β-HNA) in tetrahydrofuran (THF) solvent, which results into a multifold enhancement in the electrical properties of polystyrene (PS). A number of solutions with 0.4% of MWCNTs (w/v) and β-HNA (0–1%, w/v) in THF were prepared separately. MWCNTs precipitated out in THF solvent shortly after the preparation and formed two distinct phase regions (2φ). Gratifyingly, addition of β-HNA solution to the MWCNTs solution offered an unprecedented enhancement in the dispersion of MWCNTs. Such dispersion in solutions with only 0.02% β-HNA (w/v) was found to be stable up to 2 weeks at room temperature. FTIR spectroscopy was incorporated to illustrate the adsorption of β-HNA onto the surface of carbon nanotubes (CNTs). After this successful dispersion, nanocomposites solutions comprising of 0.067% β-HNA (w/v), 6.7% PS (w/v), and varying concentrations of MWCNTs (0–0.33%, w/v) were prepared. A remarkable dispersion behavior of MWCNTs in the presence of polymer was also observed. Finally, thin films made up of consistent polystyrene/β-HNA concentrations and increasing amounts of MWCNTs were prepared by casting technique to investigate the influence of dispersion on the electrical properties of the film. The dispersion significantly affected the DC electrical conductivity and incorporation of 5% MWCNTs elevated the electrical conductivity up to 10 orders of magnitude with respect to neat PS.