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]} (PA m PV) derivatives. A range of these PA m PV 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. PA m PV polymers solubilize SWNT bundles in organic solvents by wrapping themselves around the nanotube bundles. PA m PV 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 PA m PV 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.