Journal
CRYSTALS
Volume 9, Issue 3, Pages -Publisher
MDPI
DOI: 10.3390/cryst9030178
Keywords
NMR; cubic phase; isotropic phase; self-diffusion; liquid crystals; relaxation time; dynamics; H-1 NMR
Funding
- COST Action (EURELAX) [CA15209]
- COST Action [CA15209, ECOST-STSM-CA15209-270317-083751]
- Polish NCN project [UMO-2016/22/A/ST5/00319]
- Swedish Research Council VR
- Russian Foundation for Basic Research [17-03-00057]
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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 H-1 NMR diffusometry and H-1 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 H-1 spin-lattice relaxation time (T-1) did not show significant discontinuities at the isotropic-isotropic' phase transition. A preliminary analysis of the frequency-dependence of H-1 T-1 at different temperatures gives information about the main motional processes active in the isotropic mesophases.
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