Molecular wire formation from poly[2,7-(9,9-dioctylfluorene)-alt-(5,5′-bithiophene/cucurbit[7]uril)] polyrotaxane copolymer

The optical, electrochemical, morphology as well as surface free-energies of poly[(9,9-dioctylfluorene- alt -bithiophene/cucurbit[7]uril)] ( PF-BT•CB7 ) have been investigated and compared with those of the reference PF-BT . The absorption of PF-BT•CB7 and PF-BT extend beyond 500 nm; the maxima appear at 390 and 450 nm, respectively. The fluorescence quantum yield decreases from 0.5 for PF-BT to 0.4 for PF-BT•CB7 , while the fluorescence lifetime follow an opposite trend. The presence of the CB7 macrocycle affects the LUMO more than the HOMO one, which leads to a larger energy gap (2.72 vs 2.60 eV). Atomic force microscopy, AFM, indicated a better tendency of PF-BT•CB7 to organize into extended linear ribbons, i.e. , molecular wires, as compared to PF-BT , which arranged into short C-shaped assemblies. The advancing contact angles indicated also higher surface free-energy values for PF-BT•CB7 than PF-BT , affording materials with a slight tendency of intermolecular interactions.