Selective dipersion of single-walled carbon nanotubes with conjugated polymers

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Carbon nanotubes are a unique material composed entirely of carbon atoms bonded in a chicken-wire framework that is arranged in the shape of cylinders. In addition to their fascinating structural properties, they exhibit electrical conductivity properties that range from metallic to semiconducting, making them applicable to a number of electronic devices. Unfortunately, all methods to prepare single-walled carbon nanotubes (SWNTs) produce a mixture of both semiconducting and metallic structures, making it difficult to apply them in electronic devices that require pure samples of one type or the other. Thus, bulk-scale separation of carbon nanotubes according to their conductivity properties is a major problem that must be overcome before SWNTs can reach their full potential in commercial products. All known methods for separation of nanotubes, including density-gradient ultracentrifugation, gel filtration, and electrophoresis, result in separation on very small scale, and are achieved at high cost. However, recent results have demonstrated that electron-rich conjugated polymers can selectively interact with and disperse semiconducting SWNTs in various solvents. Unfortunately, the fundamentals of selectivity in this interaction are not understood, and metallic nanotubes have not previously been shown to be selectively dispersed by conjugated polymers. This proposal will further investigate the polymer attributes that lead to interaction selectivity with either metallic or semiconducting SWNTs, and will identify a set of polymers that can be used to achieve highly efficient, large-scale separation of the desired nanotubes. This work will be carried out in collaboration with Raymor Industries, a Canadian company that produces and sells SWNTs. This company is extremely interested in developing new ways to purify and separate SWNTs. Thus, this project will uncover fundamental underpinning of the selective interaction between conjugated polymers and different types of SWNTs, and will provide materials that are of commercial significance.