Dispersion of singlewall carbon nanotubes and preparation of polymer/singlewall carbon nanotubes composites

Abstract

Dispersion of singlewall carbon nanotubes (SWNTs) and various polymer/SWNTs composites were prepared without the formation of chemical bonding between polymer and SWNTs. Dispersions of SWNTs in various solvents and with various surfactants in water were investigated. In-situ emulsion polymerization and solution blending of surface modified SWNTs dispersions with polymer solution were used to prepare polymer/SWNTs composites. And, the physical, mechanical, electrical, and electrochemical properties of polymer/SWNTs composites were also investigated. Dispersions of SWNTs in various solvents and aqueous surfactant emulsions were investigated to correlate the degree of dispersion with Hansen solubility parameters $(δ_t^2 = δ_d^2 + δ_p^2 + δ_h^2)$. It was found the nanotubes were dispersed or suspended very well in the solvents when the dispersive component $(δ_d)$ was in a certain range. They were precipitated in the solvents with high polar component $(δ_p)$ values or hydrogen bonding component $(δ_h)$ values. The solvents in dispersed group occupied a certain region in 3-dimensional space of three solubility parameters. The surfactants with lipophilic group equal to and longer than decyl, containing 9 methylene groups and 1 methyl group, contributed to the dispersion of nanotubes in water. The surfactant in dispersed group had a lower limit in the dispersive component $(δ_d)$ of Hansen parameter. SWNTs dispersible in both water and organic solvents without oxidation and cutting nanotube threads were prepared. Polystyrene-SWNTs (PS-SWNT) composites were prepared with three different methods: miniemulsion polymerization, conventional emulsion polymerization, and mixing SWNT with PS latex. The two factors, crosslinking and surface coverage of PS are important factors for the mechanical and electrical properties, including dispersion states of SWNT in various solvents. The PS-SWNT composite prepared via a conventional emulsion polymerization showed SWNT bundles entir...