<sup>14</sup>N NMR Study of Order Fluctuations in the Isotropic Phase of Liquid Crystals

RonaldY., Dong; Tomchuk, E.; Visintainer, J. J.; Bock, E.

doi:10.1080/15421407608083875

Cited by 25 publications

(9 citation statements)

References 12 publications

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“…The linear relation suggests that critical order fluctuations exist in a seven-degree range below Tc while T t is 410_+0.5 K. Thus T t-Tc~2 K as compared with Tc-T*~.3 K [1,2]. This compares favourably with the calculations of Rao et al [10] where Tt= To+0.6 ( T c-T*) when Tc -T* ~ 1 K.…”

Section: J(pcox) Oc T~/[ ~mentioning

confidence: 50%

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N.M.R. investigation of critical orientational order fluctuations below the nematic-isotropic transition in liquid crystals

1977

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Section: J(pcox) Oc T~/[ ~mentioning

confidence: 50%

“…[1][2][3] and light-scattering [4] techniques. The Landau-de Gennes theory [5] of orientational order fluctuations has been used successfully to interpret nuclear spin relaxation above the nematic-isotropic phase transition (the clearing temperature To) which is treated as almost a second-order transition.…”

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confidence: 99%

N.M.R. investigation of critical orientational order fluctuations below the nematic-isotropic transition in liquid crystals

1977

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“…In liquid crystals, 14 N NMR resonance has so far been detected only rarely, both in lyotropic [22][23][24][25][26] and thermotropic [27,28] liquid crystals. The reason lies in the relatively large quadrupolar coupling of the 14 N nucleus, resulting in broad NMR spectra and spin-lattice relaxation times in the range of several microseconds.…”

Section: Introductionmentioning

confidence: 99%

A Photosensitive Liquid Crystal Studied by ¹⁴N NMR, ²H NMR, and DFT Calculations

et al. 2012

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An azobenzene derivative, namely diheptylazobenzene, showing the nematic and smectic A liquid crystalline phases, was investigated by means of a combined approach based on NMR and DFT calculations. (14)N NMR quadrupole- and chemical-shift-perturbed spectra were acquired in the whole mesophasic range, providing both experimental quadrupolar splittings and chemical shift anisotropy values. On the same mesogen, deuterium labelled at the α-position of the hydrocarbon chain, (2)H NMR quadrupole-perturbed spectra were recorded. The analysis of these NMR data was performed with the help of ab initio calculations, in vacuo and by taking into account the effect of the anisotropic environment typical of liquid crystals, by using the IEF-PCM model. The geometry optimizations of the azomesogen in the trans and cis configurations were performed by DFT calculations employing the combination of B3LYP functional with the 6-311G(d) basis set. The analysis of experimental NMR data was performed by considering the trans configuration as the most populated one and the corresponding quadrupolar tensors and chemical shielding tensors were determined at the DFT level of theory. The main result of this work is the determination of a relatively high and temperature-dependent molecular biaxiality of the trans state of this azomesogen.

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“…Despite its low gyromagnetic ratio and difficulty in detection, the 14 N spectrum is easily identified and less affected by liquid crystal impurities. 11 Partially deuterated DACl samples are labeled in the first three alkyl carbon sites and the last methylene and methyl groups. These samples have also been studied by 2 H NMR in its solid phases.…”

Section: Introductionmentioning

confidence: 99%

Headgroup Motion in a Lyotropic Lamellar Phase by Deuterium and Nitrogen-14 Relaxation Studies

Dong

Chen

2005

J. Phys. Chem. B

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Deuterium (2H) and nitrogen-14 (14N) NMR spectroscopy were used to investigate the molecular dynamics of a lyotropic liquid crystal. Deuterium spectral densities of motion for the C1 deuterated site on the chain of the molecule decylammonium chloride (DACl) at the Larmor frequency 61.4 MHz and those for the (14)N at the headgroup (NH(3)(+)) at 28.9 MHz are analyzed quantitatively in the lamellar phase of the DACl-d(11)/water binary system to shed light on the headgroup dynamics. The motional model used is the small step rotational diffusion for reorientations plus internal rotations of the methylene group in the strong collision limit. The tumbling motion of the long axis of the DACl molecule in the aggregates seems to be as rigorous as the molecular spinning motion, likely due to the proposed motional model. The similarity of deuterium spectral densities from the C1 and C2/C3 sites may indicate a relatively rigid unit of C1-C2-C3 in the backbone.

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¹⁴N NMR Study of Order Fluctuations in the Isotropic Phase of Liquid Crystals

Cited by 25 publications

References 12 publications

N.M.R. investigation of critical orientational order fluctuations below the nematic-isotropic transition in liquid crystals

N.M.R. investigation of critical orientational order fluctuations below the nematic-isotropic transition in liquid crystals

A Photosensitive Liquid Crystal Studied by ¹⁴N NMR, ²H NMR, and DFT Calculations

Headgroup Motion in a Lyotropic Lamellar Phase by Deuterium and Nitrogen-14 Relaxation Studies

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14N NMR Study of Order Fluctuations in the Isotropic Phase of Liquid Crystals

Cited by 25 publications

References 12 publications

N.M.R. investigation of critical orientational order fluctuations below the nematic-isotropic transition in liquid crystals

N.M.R. investigation of critical orientational order fluctuations below the nematic-isotropic transition in liquid crystals

A Photosensitive Liquid Crystal Studied by 14N NMR, 2H NMR, and DFT Calculations

Headgroup Motion in a Lyotropic Lamellar Phase by Deuterium and Nitrogen-14 Relaxation Studies

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¹⁴N NMR Study of Order Fluctuations in the Isotropic Phase of Liquid Crystals

A Photosensitive Liquid Crystal Studied by ¹⁴N NMR, ²H NMR, and DFT Calculations