title: Luminescent ethynyl-pyrene liquid crystals and gels for optoelectronic devices.
abstract: Two functional ethynyl-pyrene derivatives have been designed and synthesized by di- and tetra-substitutions of bromo pyrene derivatives with N-(4-ethynylphenyl)-3,4,5-tris(hexadecyloxy)benzamide fragments. The photoluminescence wavelength of the pyrene core can be tuned by the substitution pattern and the state of matter (solid, solution, gel, or liquid crystal). The disubstituted pyrene derivative 1 is not mesomorphic but produces robust and highly fluorescent gels in DMF, toluene, and cyclohexane. The well-defined fibers and ropes of the gel states were characterized by SEM and laser scanning confocal microscopy, and extended over several micrometers. The gels were integrated as active layers in field-effect transistors, which provided good bulk electron and hole charge mobilities as well as light emission generation. The tetra-substituted pyrene derivative is not a gelator but displays a stable liquid crystalline phase with 2D hexagonal symmetry between 20 and 200 degrees C. The pronounced luminescence properties of the mesophase allow one to observe original mesophase textures with flower-like patterns directly by fluorescence microscopy without crossed-polarizers.
authors.affiliation: Laboratoire de Chimie Organique et Spectroscopies Avancées (LCOSA), UMR 7515, CNRS-ECPM, Université de Strasbourg, 25 Rue Becquerel, 67087 Strasbourg Cedex 2, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Diring
authors.forename: Franck
authors.initials: F
authors.lastname: Camerel
authors.forename: Bertrand
authors.initials: B
authors.lastname: Donnio
authors.forename: Thierry
authors.initials: T
authors.lastname: Dintzer
authors.forename: Stefano
authors.initials: S
authors.lastname: Toffanin
authors.forename: Raffaella
authors.initials: R
authors.lastname: Capelli
authors.forename: Michele
authors.initials: M
authors.lastname: Muccini
authors.forename: Raymond
authors.initials: R
authors.lastname: Ziessel