This title appears in the Scientific Report :
2014
Please use the identifier:
http://dx.doi.org/10.1039/c3cp55303e in citations.
Vibrational Density of States of Triphenylene Based Discotic Liquid Crystals: Dependence on the Length of the Alkyl Chain
Vibrational Density of States of Triphenylene Based Discotic Liquid Crystals: Dependence on the Length of the Alkyl Chain
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 l...
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Personal Name(s): | Krause, Christina (Corresponding author) |
---|---|
Zorn, Reiner / Emmerling, Franziska / Frick, Bernhard / Huber, Patrick / Falkenhagen, Jana / Schoenhals, A. | |
Contributing Institute: |
Neutronenstreuung; ICS-1 Neutronenstreuung; JCNS-1 |
Published in: | Physical chemistry, chemical physics, 16 (2014) S. 7324 - 7333 |
Imprint: |
Cambridge
RSC Publ.
2014
|
DOI: |
10.1039/c3cp55303e |
Document Type: |
Journal Article |
Research Program: |
JCNS Soft Matter Composites |
Publikationsportal JuSER |
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. |