Chemical functionalization of Xanthan gum for the dispersion of double-walled carbon nanotubes in water

Achieving stable suspensions of carbon nanotubes (CNTs) in water is still a challenge. Addition of surfactants is desirable as it allows keeping intact the intrinsic properties of the CNTs. However, for different applications, the potential toxicity of the surfactant is an important issue. Polysaccharides are among the best candidates and chemical modification can improve their intrinsic features. They can thus combine the properties of added synthetic counterparts with their intrinsic biocompatibility. In this work, we focused on the synthesis of hydrophobically modified Xanthan (Xan) with three derivatives (Diphenylmaleic anhydride, Phtalic anhydride, Epichlorhydrin-Phenol) to disperse CNTs. The dispersion and the stability against sedimentation of double walled carbon nanotubes (DWCNTs) have been investigated (rheological properties, zeta potential) as a function of pH and Xan concentration. Our results show that stable suspension of DWCNTs for 0.5% (w/w) could be obtained with the three derivatives of modified Xanthan gum in acidic and alkaline media while Xan itself is a very poor dispersing agent for CNTs, giving good evidence of the validity of our approach.