Polymer-functionalized carbon nanotubes investigated by solid-state nuclear magnetic resonance and scanning tunneling microscopy

Carbon nanotubes are an intriguing new form of carbon, comprising molecular-scale cylinders of nanometer diameter and micrometer to centimeter lengths. They exhibit many extraordinary mechanical and electrical properties and have a wide variety of anticipated applications. However, to realize these potential applications, chemists need to develop means by which to manipulate these nanotubes in a predictable and controllable way. Novel sidewall-modified carbon nanotubes functionalized with polymers, such as poly(methyl methacrylate) (PMMA), have been prepared to gain control over the properties of nanocomposites on the molecular level. Characterization of these materials has been limited by their insolubility in organic solvents. Here the interaction between the carbon nanotube and the polymer has been studied through the use of solid-state nuclear magnetic resonance (NMR) and scanning tunneling microscopy (STM). Fast magic-angle spinning (30 kHz), to achieve high-resolution H-1 NMR, together with advanced pulse sequences such as H-1 double quantum NMR with the BABA (back-to-back) sequence, and heteronuclear H-1-C-13 sequences, are used to demonstrate the association of the initiator moieties and polymers with the surface of the nanotubes. The findings are supported by STM data of nanotubes before and after functionalization with the initiator groups.