Prediction from Molecular Shape of Solute Orientational Order in Liquid Crystals

Burnell, E. Elliott; Lange, C.A. de

doi:10.1021/cr941159v

Cited by 142 publications

(172 citation statements)

References 152 publications

Supporting

Mentioning

164

Contrasting

Order By: Relevance

“…This is most evident for Q Ã solute 0X2 in the graph for Q Ã S 0X2. This observation is consistent with the trends observed in NMR experiments which have been interpreted in terms of all solutes experiencing the same F ZZ which is taken to be a solvent property, and which is taken independent of the value of the solute quadrupole moment [1]. As the Q Ã S is increased from 0.2 to 1.0, the F Ã ZZ at the centre of solutes with zero Q Ã o values varies linearly with Q Ã S in the X S 0X740 and X S 0X960 samples, and remains zero in the X S 0X485 mixture.…”

Section: Resultssupporting

confidence: 88%

“…There exists evidence that the molecular quadrupole of small solute molecules (such as molecular hydrogen, acetylene, benzene and hexauorobenzene) plays an important role in their orientational ordering in nematic liquid crystalline solvents [1]. Estimates of the average electric ®eld gradient, F ZZ , experienced by D 2 [2,3] have been determined from deuterium NMR.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Monte Carlo simulations of zero electric field gradient liquid crystal mixtures

Burnell

Berardi²,

Syvitski

et al. 2000

Chemical Physics Letters

View full text Add to dashboard Cite

Section: Resultssupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Monte Carlo simulations of zero electric field gradient liquid crystal mixtures

Burnell

Berardi²,

Syvitski

et al. 2000

Chemical Physics Letters

View full text Add to dashboard Cite

“…The second is generally believed to be the interaction between the solute electric quadrupole moment and the solvent nonzero average electric field gradient. 3,4 In the discussion on orientational mechanisms, there are two cases that deserve special attention. One is the case of mixtures of certain nematic phases that happen to possess a zero average electric field gradient.…”

Section: Introductionmentioning

confidence: 99%

“…3 Every laboratory appears to have its own favorite model. 3,[6][7][8][9][10][11][12][13][14][15][16][17][18] In practice, the predictions of the different models show a large degree of consistency. An earlier analysis of the NMR spectrum of orientationally ordered n-pentane utilized the fact that it is a magic solute and that size-and-shape models could provide a starting point for the spectral analysis.…”

Section: Introductionmentioning

confidence: 99%

A model-free temperature-dependent conformational study of n-pentane in nematic liquid crystals

Burnell

Weber

Dong

et al. 2015

The Journal of Chemical Physics

View full text Add to dashboard Cite

The proton NMR spectra of n-pentane orientationally ordered in two nematic liquid-crystal solvents are studied over a wide temperature range and analysed using covariance matrix adaptation evolutionary strategy. Since alkanes possess small electrostatic moments, their anisotropic intermolecular interactions are dominated by short-range size-and-shape effects. As we assumed for n-butane, the anisotropic energy parameters of each n-pentane conformer are taken to be proportional to those of ethane and propane, independent of temperature. The observed temperature dependence of the n-pentane dipolar couplings allows a model-free separation between conformer degrees of order and conformer probabilities, which cannot be achieved at a single temperature. In this way for n-pentane 13 anisotropic energy parameters (two for trans trans, tt, five for trans gauche, tg, and three for each of gauche + gauche + , pp, and gauche + gauche − , pm), the isotropic trans-gauche energy difference E tg and its temperature coefficient E ′ tg are obtained. The value obtained for the extra energy associated with the proximity of the two methyl groups in the gauche + gauche − conformers (the pentane effect) is sensitive to minute details of other assumptions and is thus fixed in the calculations. Conformer populations are affected by the environment. In particular, anisotropic interactions increase the trans probability in the ordered phase. C 2015 AIP Publishing LLC. [http://dx

show abstract

“…The spectra of solutes with 8 protons or less can usually be solved with conventional techniques. 7,8 Later attempts were made to develop automated procedures. 9 More recently, for solutes with more than 8 protons, the use of novel strategies such as genetic algorithms (GAs) and evolutionary strategies (ESs) has proved extremely effective.…”

mentioning

confidence: 99%

Communication: Molecular gears

Burnell

Lange

Meerts

2016

The Journal of Chemical Physics

View full text Add to dashboard Cite

The 1H nuclear magnetic resonance spectrum of hexamethylbenzene orientationally ordered in the nematic liquid crystal ZLI-1132 is analysed using covariance matrix adaptation evolution strategy. The spectrum contains over 350 000 lines with many overlapping transitions, from which four independent direct dipolar couplings are obtained. The rotations of the six methyl groups appear to be correlated due to mutual steric hindrance. Adjacent methyl groups show counter-rotating or geared motion. Hexamethylbenzene thus behaves as a molecular hexagonal gear.

show abstract

Prediction from Molecular Shape of Solute Orientational Order in Liquid Crystals

Cited by 142 publications

References 152 publications

Monte Carlo simulations of zero electric field gradient liquid crystal mixtures

Monte Carlo simulations of zero electric field gradient liquid crystal mixtures

A model-free temperature-dependent conformational study of n-pentane in nematic liquid crystals

Communication: Molecular gears

Contact Info

Product

Resources

About