Interactions between conjugated polymers and single-walled carbon nanotubes

The chemical interactions between single walled carbon nanotubes (SWNTs) and two structurally similar polymers, poly{(m-phenylenevinylene)-co-[(2,5-dioctyloxy-p-phenylene)vinylene]}, or PmPV, and poly{(2,6-pyridinylenevinylene)-co-[(2,5-dioctyloxy-p-phenylene)vinylene]}, or PPyPV, are investigated. The fundamental difference between these two polymers is that PPyPV is a base and is readily protonated via the addition of HCl. Both polymers promote chloroform solubilization of SWNTs. We find that the SWNT/PPyPV interaction lowers the pK_a of PPyPV. Optoelectronic devices, fabricated from single polymer-wrapped SWNT structures, reveal a photogating effect on charge transport which can rectify or amplify current flow through the tubes. For PmPV wrapped tubes, the wavelength dependence of this effect correlates to the absorption spectrum of PmPV. For PPyPV, the wavelength dependence correlates with the absorption spectrum of protonated PPyPV, indicating that SWNTs assist in charge stabilization.