Orientation mechanisms for small solutes in the nematic liquid crystal 5CB-α,β-<i>d</i><sub>4</sub>

Weaver, Andrew J.; Est, A. J. Van Der; Rendell, Jennifer M; Bates, Gordon S.; Hoatson, Gina L.; Burnell, E. Elliott

doi:10.1080/02678298708086322

Cited by 30 publications

(21 citation statements)

References 12 publications

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“…It isassumed that the interaction of an external efg Fzz with the molecular quadrupole moment of the hydrogen molecule is solely responsible for the orientation of the solute. The range of sample values for the efg Fzz includes the available estimates of the external efg present in various nematic liquid crystal solvents from NMR experiments employing molecular deuterium as a probe molecule [1][2][3][4][5]28]. A number of observations that have been made before in these studies--using a gas-phase molecule model with additional simplifying assumptions about the internal and rotational motions--are confirmed by the much more advanced calculations presented here.…”

Section: Resultssupporting

confidence: 57%

Phenotypic Plasticity of Capitulum Morphogenesis in Microseris pygmaea (Asteraceae: Lactuceae)

Battjes

Bachmann

1994

Annals of Botany

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Thermal expectation values for nuclear magnetic resonance (NMR) observables for molecular hydrogen and its isotopically substituted analogues partially oriented in nematic liquid crystal solvents are calculated from first principles. High-quality nuclear wavefunctions and available data for highly correlated electronic wavefunctions at many different geometries are used from the literature. In the present description vibrational anharmonicity, centrifugal distortion, the changes of the nuclear quadrupole coupling with internuclear distance, and the dependence of the molecular quadrupole moment on the rotational quantum number have been included. The results strongly support previous conclusions that hydrogens in nematic phases are predominantly oriented through the interaction between their molecular quadrupole moment and the non-zero average external electric field gradient present in these solvents. In addition, the present theoretical results provide the basis for obtaining reliable estimates of such average external electric field gradients from a single NMR observable.

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Section: Resultssupporting

confidence: 57%

Phenotypic Plasticity of Capitulum Morphogenesis in Microseris pygmaea (Asteraceae: Lactuceae)

Battjes

Bachmann

1994

Annals of Botany

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“…The first is based on molecular shape anisotropy, similar to eq. [3], and which has been used for molecules of lower symmetry ( 5 ) . where Li is the molecular dimension, including the van der Waals radii,' along the ith axis.'…”

Section: Resultsmentioning

confidence: 99%

Orientation of some disk-shaped solutes in nematic liquid crystals

Yim¹,

Gilson²

1988

Can. J. Chem.

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The solute orientation parameters for benzene, trichloro-, and tribromobenzene have been measured, as functions of temperature, in the nematic solvents EBBA and ZLI-1132. The potential functions for orientation were derived for the model based on short and long-range contributions to the potential, with the former dependent on either a function of molecular shape or of molecular volume. There is reasonable agreement between calculated and experimental solute order parameters in both cases, and the difference in solute order parameter in the two solvents arises mainly from the difference in solvent electric field gradient.Utilisant les solvants nematiques EBBA et ZLI-1132, on a mesure les paramktres d'orientation de solute du benzkne et des trichloro-et tribromo-benzknes, en fonction de la temperature. On a obtenu les fonctions de potentiel du modkle en se basant sur les contributions au potentiel 2i courte ainsi qu'i longue distance; les premikres dependent soit de la forrne soit du volume molCculaire. Dans chacun de ces cas, on observe une bonne concordance entre les parametres calculCs et les paramktres experimentaux pour l'ordre des solutes; dans ces deux solvants, la difference dans le paramktre d'ordre du solute provient principalement de la difference dans le gradient du champ Clectrique.[Traduit par la revue] Introduction There have been numerous attempts to extend the original Maier-Saupe theory of nematic liquid crystals (1) to account for the orientation of a solute molecule dissolved in a nematic solvent, and, in particular, to relate this orientation to some molecular property of the solute. Recently, Bumell and coworkers (2-4) have proposed two approaches to this problem. The first is that the intermolecular forces responsible for the orientation of the solute arise from both short:range and longrange interactions, which depend upon the solute molecular size and shape and on the interaction of the solute molecular quadmpole moment with the electric field gradient in the solvent, respectively. The second theory (4) requires that a plot of the

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“…Weaver et al [31] investigated the temperature dependence of TCB in the pure liquid crystal 5CB, where the measured efg is non-zero. In ® gure 2 the order parameters S zz of TCB are plotted against T r , where T r is de® ned as T r = T / T NI .…”

Section: Temperature Dependence Of 135-trichlorobenzenementioning

confidence: 99%

A temperature dependence study of small solutes in zero electric field gradient nematic liquid crystal mixtures

Chandrakumar¹,

Burnell²

1997

Molecular Physics

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The temperature dependences of the proton nuclear magnetic resonance (NMR) spectra of the solutes 1,3,5-trichlorobenzene, metadichlorobenzene, orthodichlorobenzene, 1,3-bromochlorobenzene, benzene and 2-butyne have been studied in the special`zero electric ® eld gradient' mixtures 55 wt% 1132± N-(4-ethoxybenzylidene)-4 Â -n-butylaniline (EBBA) and 70 wt% (4-n-pentyl)-4 Â -cyanobiphenyl± EBBA. The order parameter matrices obtained for each solute from an analysis of the NMR spectra indicate that the solutes experience a similar anisotropic potential in both mixtures.

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Orientation mechanisms for small solutes in the nematic liquid crystal 5CB-α,β-d₄

Cited by 30 publications

References 12 publications

Phenotypic Plasticity of Capitulum Morphogenesis in Microseris pygmaea (Asteraceae: Lactuceae)

Phenotypic Plasticity of Capitulum Morphogenesis in Microseris pygmaea (Asteraceae: Lactuceae)

Orientation of some disk-shaped solutes in nematic liquid crystals

A temperature dependence study of small solutes in zero electric field gradient nematic liquid crystal mixtures

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Orientation mechanisms for small solutes in the nematic liquid crystal 5CB-α,β-d4

Cited by 30 publications

References 12 publications

Phenotypic Plasticity of Capitulum Morphogenesis in Microseris pygmaea (Asteraceae: Lactuceae)

Phenotypic Plasticity of Capitulum Morphogenesis in Microseris pygmaea (Asteraceae: Lactuceae)

Orientation of some disk-shaped solutes in nematic liquid crystals

A temperature dependence study of small solutes in zero electric field gradient nematic liquid crystal mixtures

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Product

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Orientation mechanisms for small solutes in the nematic liquid crystal 5CB-α,β-d₄