May 15, 2014 - Hans-Jürgen Butt & Klaus Müllen & George Floudas. Received: 2 ...... Seiberle H, Stille W, Strobl G (1990) Macromolecules 23:2007â2016. 36.
Switchable dielectric permittivity with temperature and Dc-bias in a semifluorinated azobenzene derivative René Stangenberg, Christos Grigoriadis, Hans-Jürgen Butt, Klaus Müllen & George Floudas Colloid and Polymer Science Kolloid-Zeitschrift und Zeitschrift für Polymere ISSN 0303-402X Volume 292 Number 8 Colloid Polym Sci (2014) 292:1939-1948 DOI 10.1007/s00396-014-3217-9
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Author's personal copy Colloid Polym Sci (2014) 292:1939–1948 DOI 10.1007/s00396-014-3217-9
ORIGINAL CONTRIBUTION
Switchable dielectric permittivity with temperature and Dc-bias in a semifluorinated azobenzene derivative René Stangenberg & Christos Grigoriadis & Hans-Jürgen Butt & Klaus Müllen & George Floudas
Received: 2 February 2014 / Revised: 27 March 2014 / Accepted: 28 March 2014 / Published online: 15 May 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract The thermodynamic, optical, structural, and dynamic properties of the semifluorinated (E)-1-(4-octylphenyl)2-(4-(perfluorooctyl)phenyl)diazene (4) and the corresponding (E)-1,2-bis(4-octylphenyl)diazene (5) have been studied with differential scanning calorimetry, polarizing optical microscopy, X-ray diffraction, and dielectric spectroscopy. 4 combines the azobenzene properties with the fluorophobic effect and gives rise to a responsive material with a temperature and dc-bias-driven switchable dielectric permittivity within the narrower nematic phase. This is caused by the nematic potential that inevitably brings some fluorocarbon chains in proximity to the hydrocarbon chains from adjacent molecules. Frustration is alleviated by reducing the nematic-to-isotropic transition temperature and by increasing the crystalline-to-nematic transition temperature, thus limiting the stability of the nematic phase. Unlike the normal isotropic phase of compound 5, the isotropic phase of compound 4 contains dipoles with short-range orientation correlations. Optimizing the type of interactions may result in materials with applications as molecular switches and electrooptic devices.
Dedicated to Prof. Friedrich Kremer on the occasion of his 65th birthday. Electronic supplementary material The online version of this article (doi:10.1007/s00396-014-3217-9) contains supplementary material, which is available to authorized users. R. Stangenberg : H.
