%0 Journal Article
%A Krause, Christina
%A Zorn, Reiner
%A Emmerling, Franziska
%A Frick, Bernhard
%A Huber, Patrick
%A Falkenhagen, Jana
%A Schoenhals, A.
%T Vibrational Density of States of Triphenylene Based Discotic Liquid Crystals: Dependence on the Length of the Alkyl Chain
%J Physical chemistry, chemical physics
%V 16
%@ 1463-9084
%C Cambridge
%I RSC Publ.
%M FZJ-2014-01675
%P 7324 - 7333
%D 2014
%X 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.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000333523500019
%R 10.1039/c3cp55303e
%U https://juser.fz-juelich.de/record/151796