Effective dispersion of multi-walled carbon nanotubes in aqueous solution using an ionic-gemini dispersant

A promising ionic-gemini molecule, 4, 4'-di (n-tetradecyl) diphenylmethane disulfate salt (DSDM), is reported for effective dispersion of multi-walled carbon nanotubes (MWCNTs) in aqueous medium in the present investigation. The dispersibility and stability of the DSDM-modified MWCNTs were characterized by UV-vis spectrophotometer, Raman spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy and zeta potential measurements. The hydrophobic interaction between alky chains and carbon nanotubes as well as the π-π-stacking interaction between benzene rings and carboatomic rings in MWCNTs enables a successful modification of DSDM onto the MWCNT surface. The dispersed MWCNTs individually existed in dispersion with no structural damage, indicating a much better performance than the MWCNTs dispersed by the sodium dodecylbenzene sulfonate (SDBS), a frequently reported single-chain ionic dispersant. Surface potential measurements showed that the DSDM-modified MWCNTs were negatively charged, giving rise to electrostatic repulsion between the MWCNTs in aqueous solution. A better MWCNT dispersion effect was observed with the increase in MWCNT surface potential, and the dispersion with high MWCNT surface potential presents high dispersion stability with no agglomeration appeared for more than 5 months. The magnesium (Mg) matrix composite fabricated based on the DSDM-dispersed MWCNTs demonstrated excellent mechanical properties compared to pure Mg. Our research may provide an alternative way to improve the mechanical properties of composites.