Orientational order of guest molecules in aligned liquid crystal as measured by EPR and UV-vis techniquesстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 25 сентября 2013 г.
Аннотация:Orientational order of guest molecules in aligned liquid crystal 4-cyano-4-pentylbiphenyl (5CB) is studied viaoptical dichroism and electron paramagnetic resonance (EPR) spectra measurements. The guest molecules usedare bifunctional molecules bearing paramagnetic nitroxide group and photochromic azobenzene moiety. Thebifunctional probe with rigidly bonded nitroxide and azobenzene moieties was found to align as a whole, whileflexible long spacer between the moieties provides independent alignment for the nitroxide and azobenzeneparts. Intermolecular interactions responsible for the alignment of azobenzene and nitroxide moieties of theprobe molecules are discussed. The molecules with cis-configuration of azobenzene moiety are able to align inthe liquid-crystalline medium, but to a lesser extent than the molecules with trans-configuration. Directions oforientational axes and characteristics of rotational mobility of spin probes are determined. Second, fourth and, insome cases, sixth rank order parameter values are found.