Filtern
Erscheinungsjahr
- 2017 (1)
Dokumenttyp
- Vortrag (1) (entfernen)
Sprache
- Englisch (1)
Referierte Publikation
- nein (1) (entfernen)
Schlagworte
- Dicotic liquid crystals (1) (entfernen)
Eingeladener Vortrag
- nein (1)
Discotic liquid crystals (DLCs) are self-assembled materials where self-assembly is driven by non-covalent intermolecular interactions. The corresponding molecules consist of a flat and rigid aromatic core substituted by flexible aliphatic side chains. While the former is responsible for the π-stacking, the latter gives rise to an increased solubility, processability, and rich thermotropic behavior. The disc-shaped molecules form columns that further assemble into two-dimensional arrays with a hexagonal mesophase. The alkyl chains fill the intracolumnar space giving rise to a nanophase separated state. These soft matter materials with highly ordered columnar structures have a great potential in molecular electronic devices such as active semiconductors in organic field-effect transistors and photovoltaic devices with a charge carrier mobility of up to 1.1 cm2/Vs. Two different homologous systems based on triphenylene derivatives were investigated as model systems for DLCs where the length of the aliphatic side chains is widely varied. Structural information is retrieved by X-ray diffraction carried out on a synchrotron. Experiments were carried out in the bulk state and confined to the nanometer wide channels of anodic aluminum membranes (Pore diameter 20 nm, 40nm, 80 nm and 180 nm). The latter case can be considered as a promising way to prepare nanowires. As method broadband dielectric spectroscopy (frequency range 10-2 Hz to 109 Hz) is employed. These experiments were accompanied by thermal investigations (Differential Scanning Calorimetry as well as Thermogravimetric Analysis) as well as inelastic neutron scattering (neutron Time-of-Flight and neutron Backscattering). The dynamics of these unique soft matter materials are discussed in detail considering their structure (length of the aliphatic side chain), the effect of self-confinement (of the aliphatic chains in the intracolumnar space) and of the outer confinement (influence of the pore size). Comparison is further made to a pyrene based system.