Liquid-Crystalline Samples: Static and Dynamic Measurements of Director Alignment

Sugimura, Akihiko; Luckhurst, G. R.

doi:10.1002/9780470034590.emrstm1321

Cited by 2 publications

(4 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our time-resolved NMR experiments have shown another surprising result, namely, the nonuniformity in the director distribution grows as the time taken to align the nematic with the magnetic field, prior to the application of the electric field, is reduced [1]. In other words, the longer the MPT, the more uniform the director distribution will be at the start of the turn-on experiment.…”

Section: Resultsmentioning

confidence: 83%

“…6 of Ref. [1]). It would seem that this relaxation time is remarkably long in comparison with that needed to align the director distribution by the magnetic field, predicted by the torque-balance equation.…”

Section: Resultsmentioning

confidence: 87%

“…Such macroscopic behavior has been investigated using deuterium nuclear magnetic resonance ( 2 H NMR) spectroscopy. Here the director is aligned by the magnetic field of the spectrometer, and the application of an electric field produces a nonequilibrium state, resulting in rotation of the director [1,2]. This powerful technique has proved to be especially important for the investigation of director alignment in liquid crystals [3][4][5][6][7].…”

Section: Introductionmentioning

confidence: 98%

“…This can be manipulated by external factors, including homogeneous electric and magnetic as well as inhomogeneous surface fields. It is therefore of prime importance to understand the alignment of the nematic director by either a magnetic and/or an electric field by careful evaluation of the hydrodynamic processes under both equilibrium and nonequilibrium conditions [1]. To complement these experiments, many theoretical models, based on continuum theory, have been developed that successfully describe the static and dynamic phenomena.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Macroscopic order in a nematic liquid crystal: Perturbation by spontaneous director fluctuations

et al. 2015

Self Cite

View full text Add to dashboard Cite

The dynamic alignment of the nematic director by near-orthogonal electric and magnetic fields has been investigated. The intermediate states during the relaxation process were found, with the aid of time-resolved deuterium NMR spectroscopy, to be markedly nonuniform. The macroscopic order was perturbed, although the initial and final states of the director appear to be essentially uniform. However, the initial state does have a profound influence on the uniformity of the director in the intermediate states. We have developed a fundamental model based on the effect of spontaneous director fluctuations to explain these unusual NMR observations.

show abstract

Section: Resultsmentioning

confidence: 83%

Section: Resultsmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Macroscopic order in a nematic liquid crystal: Perturbation by spontaneous director fluctuations

et al. 2015

Self Cite

View full text Add to dashboard Cite

show abstract

Anhydrous octyl-glucoside phase transition from lamellar to isotropic induced by electric and magnetic fields

Hashim

Sugimura

Nguan

et al. 2017

The Journal of Chemical Physics

View full text Add to dashboard Cite

A static deuterium nuclear magnetic resonance (HNMR) technique (magnetic field, B = 7.05 T) was employed to monitor the thermotropic lamellar phase of the anhydrous 1:1 mixture sample of octyl-b-D-glucoside (βOG) and that of partially deuterium labelled at the alpha position on the chain, i.e.,βOG-d In the absence of an electric field, the H NMR spectrum of the mixture gives a typical quadrupolar doublet representing the aligned lamellar phase. Upon heating to beyond the clearing temperature at 112 °C, this splitting converts to a single line expected for an isotropic phase. Simultaneous application of magnetic and electric fields (E = 0.4 MV/m) at 85 °C in the lamellar phase, whose direction was set to be parallel or perpendicular to the magnetic field, resulted in the change of the doublet into a single line and this recovers to the initial doublet with time for both experimental geometries. This implies E- and B-field-induced phase transitions from the lamellar to an isotropic phase and a recovery to the lamellar phase again with time. Moreover, these phase transformations are accompanied by a transient current. A similar observation was made in a computational study when an electric field was applied to a water cluster system. Increasing the field strength distorts the water cluster and weakens its hydrogen bonds leading to a structural breakdown beyond a threshold field-strength. Therefore, we suggest the observed field-induced transition is likely due to a structure change of the βOG lamellar assembly caused by the field effect and not due to Joule heating.

show abstract

Liquid-Crystalline Samples: Static and Dynamic Measurements of Director Alignment

Cited by 2 publications

References 34 publications

Macroscopic order in a nematic liquid crystal: Perturbation by spontaneous director fluctuations

Macroscopic order in a nematic liquid crystal: Perturbation by spontaneous director fluctuations

Anhydrous octyl-glucoside phase transition from lamellar to isotropic induced by electric and magnetic fields

Contact Info

Product

Resources

About