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Open AccessArticle

Study of Liquid Crystals Showing Two Isotropic Phases by 1H NMR Diffusometry and 1H NMR Relaxometry

1
Department of Solid State Physics, Jožef Stefan Institute, SI-1000 Ljubljana, Slovenia
2
Dipartimento di Chimica e Chimica Industriale, Università di Pisa, 56124 Pisa, Italy
3
Department of Chemistry, University of Warsaw, 02-093 Warsaw, Poland
4
Department of Chemistry, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden
5
Laboratory of Biomolecular NMR, St. Petersburg 198504, Russia
*
Author to whom correspondence should be addressed.
Crystals 2019, 9(3), 178; https://doi.org/10.3390/cryst9030178
Received: 24 February 2019 / Revised: 21 March 2019 / Accepted: 23 March 2019 / Published: 26 March 2019
(This article belongs to the Special Issue Nuclear Magnetic Resonance of Liquid Crystals)
In this work, we report a study of two thermotropic liquid crystalline samples showing a not common mesophase behavior. The samples, namely a di-benzyloxy biphenyl derivative labelled 9/2 RS/RS, and a bimesogenic liquid crystal labelled L1, show a direct transition between two isotropic phases followed, at lower temperatures, by the optically isotropic, 3D structured, cubic phase. These systems have been investigated by means of 1H NMR diffusometry and 1H NMR relaxometry in order to characterize their isotropic–isotropic’–cubic mesophase behavior, mainly on the dynamic point of view. In particular, the temperature trend of the self-diffusion coefficients measured for both samples allowed us to significantly distinguish between the two isotropic phases, while the temperature dependence of the 1H spin-lattice relaxation time (T1) did not show significant discontinuities at the isotropic–isotropic’ phase transition. A preliminary analysis of the frequency-dependence of 1H T1 at different temperatures gives information about the main motional processes active in the isotropic mesophases. View Full-Text
Keywords: NMR; cubic phase; isotropic phase; self-diffusion; liquid crystals; relaxation time; dynamics; 1H NMR NMR; cubic phase; isotropic phase; self-diffusion; liquid crystals; relaxation time; dynamics; 1H NMR
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Gradišek, A.; Cifelli, M.; Wojcik, M.; Apih, T.; Dvinskikh, S.V.; Gorecka, E.; Domenici, V. Study of Liquid Crystals Showing Two Isotropic Phases by 1H NMR Diffusometry and 1H NMR Relaxometry. Crystals 2019, 9, 178.

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