title: The effect of permodified cyclodextrins encapsulation on the photophysical properties of a polyfluorene with randomly distributed electron-donor and rotaxane electron-acceptor units.
abstract: We report on the synthesis as well as the optical, electrochemical and morphological properties of two polyrotaxanes (4a and 4b), which consist of electron-accepting 9,9-dicyanomethylenefluorene 1 as an inclusion complex in persilylated β- or γ-cyclodextrin (TMS-β-CD, TMS-γ-CD) (1a, 1b) and methyltriphenylamine as an electron-donating molecule. They are statistically distributed into the conjugated chains of 9,9-dioctylfluorene 3 and compared with those of the corresponding non-rotaxane 4 counterpart. Rotaxane formation results in improvements of the solubility, the thermal stability, and the photophysical properties. Polyrotaxanes 4a and 4b exhibited slightly red-shifted absorption bands with respect to the non-rotaxane 4 counterpart. The fluorescence lifetimes of polyrotaxanes follow a mono-exponential decay with a value of τ = 1.14 ns compared with the non-rotaxane, where a bi-exponential decay composed of a main component with a relative short time of τ1 = 0.88 (57.08%) and a minor component with a longer lifetime of τ2 = 1.56 ns (42.92%) were determined. The optical and electrochemical band gaps (ΔE g) as well as the ionization potential and electronic affinity characterized by smaller values compared to the values of any of the constituents. AFM reveals that the film surface of 4a and 4b displays a granular morphology with a lower dispersity supported by a smaller roughness exponent compared with the non-rotaxane counterpart.
authors.affiliation: Inorganic Polymers, ''Petru Poni'' Institute of Macromolecular Chemistry, Grigore Ghica Voda Alley, 700487 Iasi, Romania.
authors.forename: Aurica
authors.initials: A
authors.lastname: Farcas
authors.affiliation: Inorganic Polymers, ''Petru Poni'' Institute of Macromolecular Chemistry, Grigore Ghica Voda Alley, 700487 Iasi, Romania.
authors.forename: Ana-Maria
authors.initials: AM
authors.lastname: Resmerita
authors.affiliation: Laboratoire de Physicochimie des Polymères et des Interfaces (EA 2528), Institut des Matériaux, Université de Cergy-Pontoise, F-95031 Cergy-Pontoise Cedex, France.
authors.forename: Pierre-Henri
authors.initials: PH
authors.lastname: Aubert
authors.affiliation: "Gh. Asachi" Technical University, 61-63 Mangeron Blvd, 700050 Iasi, Romania.
authors.forename: Flavian
authors.initials: F
authors.lastname: Farcas
authors.affiliation: Inorganic Polymers, ''Petru Poni'' Institute of Macromolecular Chemistry, Grigore Ghica Voda Alley, 700487 Iasi, Romania.
authors.forename: Iuliana
authors.initials: I
authors.lastname: Stoica
authors.affiliation: Inorganic Polymers, ''Petru Poni'' Institute of Macromolecular Chemistry, Grigore Ghica Voda Alley, 700487 Iasi, Romania.
authors.forename: Anton
authors.initials: A
authors.lastname: Airinei
keywords: cyclodextrins; energy band gaps; fluorescence lifetimes; persilylated cyclodextrins; supramolecular encapsulation; surface morphology