TY - CONF A1 - Sentker, K. A1 - Yildirim, Arda A1 - Zantop, A. A1 - Lippmann, M. A1 - Hofmann, T. A1 - Seeck, O. A1 - Kityck, A. A1 - Mazza, M. A1 - Schönhals, Andreas A1 - Huber, P. T1 - Characterization of the thermotropic phase behavior and microscopic structure of a confined discotic liquid crystal N2 - Discotic liquid crystals (DLC) filled into cylindrical nanopores exhibit a liquid crystalline phase with their molecules arranged in hexagonal columns. The columns orient perpendicular (radially) or parallel (axially) with respect to the pore axis depending on surface anchoring conditions and pore size. Axially oriented columns enable the fabrication of organic nanowires utilizing the high conductivity in the stacking direction due to overlapping π-electrons. This leads to interesting applications in e.g. organic semiconductorbased devices. The molecular ordering of the liquid crystalline columns can be probed by temperature dependent optical retardation measurements supplemented by X-ray diffraction sensitive to the translational order. We investigated the DLC 2, 3, 6, 7, 10, 11 - hexakis [hexyloxy] triphenylene (HAT6) embedded in nanoporous alumina and silica membranes as function of the pore diameter (12 nm - 180 nm). Due to their hydrophilic nature porous membranes enforce face-on anchoring leading to a radial orientation. To obtain edge-on anchoring conditions, and thus favoring axial orientation, the silica membrane surface is chemically modified. The optical retardation measurements show that the columns orient radially in these membranes independent of the anchoring conditions. Interestingly, a quantized phase transition of each molecular layer is found indicated by a distinct increase of the optical orientation. Additionally, an axial orientation of HAT6 filled into alumina membranes with a pore diameter of 25 nm is achieved. A Landau-de Gennes ansatz semi-quantitatively describes the phase transition behavior observed. X-ray diffraction experiments performed at the 3rd generation synchrotron radiation source PETRA III at DESY giving detailed information about the translational order support these findings. Summarizing, this study shows the existence of a phase transition in the molecular range as well as the suitability of the membrane with 25 nm pores as a template for preparing organic nanowires. T2 - Liquids 2017 – 10th Liquid Matter Conference CY - Ljubljana, Slovenia DA - 17.07.2017 KW - Discotic Liquid Crystals PY - 2017 AN - OPUS4-41180 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -