Noncovalent side-wall functionalization of single-walled carbon nanotubes

A family of poly[(m-phenylenevinylene)-co-(p-phenylenevinylene)]s, functionalized in the synthetically accessible C-5 position of the meta-disubstituted phenylene rings have been designed and synthesized: they are essentially poly{(5-alkoxy-m-phenylenevinylene)-co-[(2,5-dioctyloxy-p-phenylene)-vinylene]} (PAmPV) derivatives. A range of these PAwPV polymers have been prepared both (1) by the polymerization of O-substituted 5-hydroxyisophthaldehydes and (2) by chemical modifications carried out on polymers bearing reactive groups at the C-5 positions. PAmPV polymers solubilize SWNT bundles in organic solvents by wrapping themselves around the nanotube bundles. PAmPV derivatives which bear tethers or rings form pseudorotaxanes with rings and threads, respectively. The formation of the polypseudorotaxanes has been investigated in solution by NMR and UV/vis spectroscopies, as well as on silicon oxide wafers in the presence of SWNTs by AFM and surface potential microscopy. Wrapping of these functionalized PAmPV polymers around SWNTs results in the grafting of pseudorotaxanes along the walls of the nanotubes in a periodic fashion. The results hold out the prospect of being able to construct arrays of molecular switches and actuators.