Aqueous dispersion of pristine single-walled carbon nanotubes prepared by using a vinylimidazole-based polymer dispersant

Abstract

In most practical applications, actualizing the inherent properties of single-walled carbon nanotubes (SWNTs) depends strongly on the exfoliation and dispersion of SWNT bundles as individuals and/or small-diameter bundles in various liquid media. Aqueous dispersions are of specific interest in many ways, and polymer dispersants prove to be quite competent for such tasks. To develop a new type of polymer dispersant with accessional function, four water-soluble vinylimidazole (VI)-based polymers bearing different pendant groups were designed, synthesized, and then tested for preparation of aqueous dispersions of pristine SWNTs. The dispersing efficiency was studied as functions of molecular structure and solution nature of VI-polymer. Under assistance of VI-polymers, stable aqueous dispersions are available: the maximal dispersibility reaches 148.9 mg l⁻¹, while initial amount of optimal VI-polymer is merely 0.06 mg ml⁻¹ (∼6 × 10⁻³ wt%), far below ∼1.0 wt% of sodium dodecyl sulfate (SDS), the most commonly used surfactant, for achieving SWNT dispersion. Biocompatibility of VI-polymer–SWNT complexes obtained from pertinent aqueous dispersions was assessed by culturing L929 cells (mouse fibroblasts), and the results showed that the complex materials were non-toxic to the cells under consideration. The ready dispersions thus pave the way for a variety of applications including those with biological relevance, wherein SWNTs have to face the water-based chemical environments. Besides, it may be more important that the findings, i.e. amphiphilicity and free/sparse of polymer-micelles are two critical factors for VI-polymer to determine its dispersing efficiency, can be potentially applicable to other nanotube/dispersant systems and serve as a common model for developing aqueous dispersions of pristine nanotubes.