Polymer-Assisted Isolation of Single Wall Carbon Nanotubes in Organic Solvents for Optical-Quality Nanotube-Polymer Composites

Dispersions of isolated single wall carbon nanotubes (SWNTs) in pure organic solvents can usually be prepared only at low concentrations (∼0.01-0.02 g/L). Here, we use poly(vinylpyrrolidone) as a dispersant for unfunctionalized SWNTs in N-methyl-2-pyrrolidone and achieve concentrations of up to ∼0.16 g/L. Such dispersions remain stable by visual inspection for at least 1 year after preparation. Well-resolved features in the absorption spectra are observed, implying the presence of isolated SWNTs or small bundles. This is further confirmed by photoluminescence excitation spectroscopy. Dispersions enriched with isolated SWNTs are obtained by ultracentrifugation. Strong photoluminescence signal from nanotubes with ∼1 nm diameter indicates the dispersion mechanism to be diameter selective. SWNT-polymer composites prepared from filtered dispersions, with styrene methyl methacrylate (SMMA) as host matrix, are obtained with sub-micrometer aggregations and high optical density. The high transparency of SMMA below 1650 nm is promising when such SWNT-polymer composites are to be used in telecommunication applications.