Nanostructured Macromolecules and Carbon-based Materials

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This proposal aims to investigate the selective interactions between conjugated polymers and single-walled carbon nanotubes (SWNTs). Currently, the enormous technological promise of SWNTs in numerous applications, ranging from flexible touch screens to sensors for traces of explosives or toxins, cannot be realized on commercial scale because of difficulty in purifying, isolating, and dispersing specific nanotube types. Recently, it has been demonstrated that conjugated polymers can bind to the surface of SWNTs, producing complexes that exhibit solubility and enhanced purity. This approach to nanotube purification is promising as it can be easily and cost-effectively scaled up to industrial levels. We have recently shown that the electronic properties of conjugated polymers can dictate their preference for interacting with semiconducting (s) versus metallic (m) SWNTs. While electron-rich polymers prefer s-SWNTs, electron-poor polymers show a preference for m-SWNTs. Now the challenge is to increase the purity of m-SWNTs being dispersed by making conjugated polymers that are as electron-poor as possible, which is one of the goals of this proposal. This will be accomplished by decorating the polymer backbone with electron-withdrawing groups. We will also investigate methods by which conjugated polymers can be removed from the SWNT surface after selective interactions and separation/purification of nanotubes have taken place. This will be done by preparing degradable polymers that bind to the SWNT surface, and then can be depolymerized back to their original monomer components (which can be recycled). In addition, we will explore fundamental questions about the type of polymer structure that is needed for optimal interactions with SWNTs, with particular focus on whether conjugated polymers are actually required. We will prepare new structures that contain conjugated units separated by non-conjugated segments, and will optimize the interactions of these polymers with SWNTs. Finally, we will attach molecular recognition elements to the SWNT surface through supramolecular interactions with conjugated polymers in order to impart sensory properties to the resulting assemblies. Sensor devices will be prepared, and their response to specific analytes of interest in defence and law enforcement applications will be measured.