Phase transitions in a high magnetic field of an odd, symmetric liquid crystal dimer having two nematic phases, N_{U} and N_{TB}, studied by NMR spectroscopy

Physical Review. E
C T ImrieG R Luckhurst

Abstract

Both ^{1}H and ^{13}C NMR spectra have been obtained in a static magnetic field of 23.5 T on a bent-shaped dimer molecule, 1^{''},7^{''}-bis(4-cyanobiphenyl-4'-yl) nonane (CB9CB), which shows the sequence of liquid crystal phases twist-bend nematic, N_{TB}, and uniaxial nematic, N_{U}, before entering the isotropic phase. The ^{1}H spectra are used to locate the temperature at which the sample melts to form a twist-bend nematic, T_{CrN_{TB}}, and then T_{N_{U}I} when the isotropic phase is entered, both in a magnetic field of 23.5 T, and to compare these with those measured at the Earth's field. The differences between these transition temperatures are found to be zero within the error in their measurement, in stark contrast to previous measurements by Salili et al. [Phys. Rev. Lett. 116, 217801 (2016)10.1103/PhysRevLett.116.217801]. In the isotropic phase in the presence of the field the sample exists in a paranematic phase in which the molecules of CB9CB are partially ordered. The ^{1}H and ^{13}C NMR spectra in the paranematic phase are used to measure the critical temperature T* below which this phase is unstable. The spectra are also used to study the structure, molecular orientational order, and distribution of molecular ...Continue Reading

References

Apr 12, 2006·Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics·D WiantS Sprunt
Jul 13, 2006·The Journal of Physical Chemistry. a·Denis MerletJames W Emsley
Dec 31, 2008·Physical Review Letters·T OstapenkoJ T Gleeson
Dec 21, 2011·Physical Review Letters·Oriano FrancescangeliEdward T Samulski
Feb 4, 2014·Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics·T B T ToG R Luckhurst
May 16, 2014·Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics·Nababrata GhoshalSoumen Kumar Roy
Jul 15, 2015·Journal of Magnetic Resonance·L M HeistM Lelli
Jun 2, 2016·Progress in Nuclear Magnetic Resonance Spectroscopy·Jean Jeener, Gerrit Alewaeters

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