Aqueous Dispersions of Single-wall and Multiwall Carbon Nanotubes with Designed Amphiphilic Polycations

Abstract

Poor solubility of single-walled and multiwalled carbon nanotubes (NTs) in water and organic solvents presents a considerable challenge for their purification and applications. Macromolecules can be convenient solubilizing agents for NTs and a structural element of composite materials for them. Several block copolymers with different chemical functionalities of the side groups were tested for the preparation of aqueous NT dispersions. Poly(N-cetyl-4-vinylpyridinium bromide-co-N-ethyl-4-vinylpyridinium bromide-co-4-vinylpyridine) was found to form exceptionally stable NT dispersions. It is suggested that the efficiency of macromolecular dispersion agents for NT solubilization correlates with the topological and electronic similarity of polymer-NT and NT-NT interactions in the nanotube bundles. Raman spectroscopy and atomic force and transmission electron microcopies data indicate that the polycations are wrapped around NTs forming a uniform coating 1.0-1.5 nm thick. The ability to wind around the NT originates in the hydrophobic attraction of the polymer backbone to the graphene surface and topological matching. Tetraalkylammonium functional groups in the side chains of the macromolecule create a cloud of positive charge around NTs, which makes them hydrophilic. The prepared dispersions could facilitate the processing of the nanotubes into composites with high nanotube loading for electronic materials and sensing. Positive charge on their surface is particularly important for biological and biomedical applications because it strengthens interactions with negatively charged cell membranes. A high degree of spontaneous bundle separation afforded by the polymer coating can also be beneficial for NT sorting.

Preparation of multiwall carbon nanotubes (MWCNTs) stabilised by highly branched hydrocarbon surfactants and dispersed in natural rubber latex nanocomposites

“…Furthermore, an increase in the I D /I G ratio for MWCNTs/ NR-latex was also observed as a consequence of the wrapping process by isoprene monomers in the NRlatex [45]. We confirmed that the surfactant treatments used in this study did not disturb the π-systems of the MWCNTs in the nanocomposites.…”

Aggregate structure of hydroxyproline-rich glycoprotein (HRGP) and HRGP assisted dispersion of carbon nanotubes

“…But most applications require well-dispersed SWNT systems in order to take advantage of the unique properties. Many surfactants such as lipids, sugars, proteins, DNA, commodity polymers, and designed polymers have been used to facilitate the dispersion of SWNTs [20][21][22][23][24][25][26]. Given the amphiphilicity of YK20, we examined the SWNT dispersing properties of YK20 in solution.…”

Advances in liquid crystalline nano-carbon materials: preparation of nano-carbon based lyotropic liquid crystal and their fabrication of nano-carbon fibers with liquid crystalline spinning

“…Up to now, three methods have been used to prepare liquid crystalline CNTs: acid oxidation [24,25], polymer wrapping [26][27][28][29], and superacid protonation [30,31]. Acid oxidation is an efficient method of modifying the CNT surface by introducing functional groups [32][33][34][35].…”