High-resolution dielectric study reveals pore-size-dependent orientational order of a discotic liquid crystal confined in tubular nanoporesReport as inadecuate




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1 Czestochowa University Technology 2 IPR - Institut de Physique de Rennes 3 BAM Bundesanstalt für Materialforschung u. -prüfung 4 TUHH - Technische Universität Hamburg-Harburg

Abstract : We report a high-resolution dielectric study on a pyrene-based discotic liquid crystal DLC in the bulk state and confined in parallel tubular nanopores of monolithic silica and alumina membranes. The positive dielectric anisotropy of the DLC molecule at low frequencies in the quasistatic case allows us to explore the thermotropic collective orientational order. A face-on arrangement of the molecular discs on the pore walls and a corresponding radial arrangement of the molecules is found. In contrast to the bulk, the isotropic-to-columnar transition of the confined DLC is continuous, shifts with decreasing pore diameter to lower temperatures, and exhibits a pronounced hysteresis between cooling and heating. These findings corroborate conclusions from previous neutron and x-ray-scattering experiments as well as optical birefringence measurements. Our study also indicates that the relative simple dielectric technique presented here is a quite efficient method in order to study the thermotropic orientational order of DLC-based nanocomposites.





Author: Sylwia Całus - Andriy V. Kityk - Lech Borowik - Ronan Lefort - Denis Morineau - Christina Krause - Andreas Schönhals - Mark Bus

Source: https://hal.archives-ouvertes.fr/



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