Raman scattering evidence of instantaneous nanoscale order in liquids and plastic crystals

Malinovsky, V. K.; Surovtsev, N. V.

doi:10.1002/pssc.200405309

Cited by 4 publications

(1 citation statement)

References 19 publications

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“…12 To elucidate the controversy on the BP several studies have been carried out by means of Fourier transform infrared spectroscopy, inelastic X-ray scattering, neutron scattering, Mo ¨ssbauer spectroscopy, low frequency Raman spectroscopy and light scattering on conventional glass formers such as low molecular weight liquids and polymers. [13][14][15][16][17][18][19][20] This concerns also biologically active systems such as proteins 21 which are also considered to undergo a glass transition. As discussed above a detailed theoretical description of the boson peak is not developed untill now, the connection of the Boson peak to fluctuations of elastic constants has been demonstrated in ref.…”

Section: Introductionmentioning

confidence: 99%

Vibrational density of states of triphenylene based discotic liquid crystals: dependence on the length of the alkyl chain

Krause

Zorn

Emmerling

et al. 2014

Phys. Chem. Chem. Phys.

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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.

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