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Publisher DOI: 10.1039/C3CP55303E
Title: Vibrational density of states of triphenylene based discotic liquid crystals: dependence on the length of the alkyl chain
Language: English
Authors: Krause, Christina 
Zorn, Reiner 
Emmerling, Franziska 
Falkenhagen, Jana 
Frick, Bernhard 
Huber, Patrick 
Schönhals, Andreas 
Issue Date: 2014
Publisher: Royal Society of Chemistry (RSC)
Source: Phys. Chem. Chem. Phys. 16 (16): 7324-7333 (2014)
Journal or Series Name: Physical chemistry, chemical physics 
Abstract (english): The vibrational density of states of a series of homologous triphenylene-based discotic liquid crystals HATn (n = 5, 6, 8, 10, 12) depending on the length of the aliphatic side chain is investigated by means of inelastic neutron scattering. All studied materials have a plastic crystalline phase at low temperatures, followed by a hexagonally ordered liquid crystalline phase at higher temperatures and a quasi isotropic phase at the highest temperatures. The X-ray scattering pattern for the plastic crystalline phase of all materials shows a sharp Bragg reflection corresponding to the intercolumnar distance in the lower q-range and a peak at circa 17 nm 1 related to intracolumnar distances between the cores perpendicular to the columns as well as a broad amorphous halo related to the disordered structure of the methylene groups in the side chains in the higher q-range. The intercolumnar distance increases linearly with increasing chain length for the hexagonal columnar ordered liquid crystalline phase. A similar behaviour is assumed for the plastic crystalline phase. Besides n = 8 all materials under study exhibit a Boson peak. With increasing chain length, the frequency of the Boson peak decreases and its intensity increases. This can be explained by a self-organized confinement model. The peaks for n = 10, 12 are much narrower than for n = 5, 6 which might imply the transformation from a rigid system to a softer one with increasing chain length. Moreover the results can also be discussed in the framework of a transition from an uncorrelated to a correlated disorder with increasing n where n = 8 might be speculatively considered as a transitional state.
DOI: 10.15480/882.2187
ISSN: 1463-9084
Institute: Werkstoffphysik und -technologie M-22 
Type: (wissenschaftlicher) Artikel
License: CC BY-NC 3.0 (Attribution-NonCommercial) CC BY-NC 3.0 (Attribution-NonCommercial)
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