Smectic layering at the free surface of liquid crystals in the nematic phase: X-ray reflectivity

Pershan, Peter S.; Braslau, A.; Weiss, A. H.; Als‐Nielsen, J.

doi:10.1103/physreva.35.4800

Cited by 150 publications

(57 citation statements)

References 22 publications

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“…3͑a͔͒ with a small change in x-ray energy as a function of the incident angle on the sample. This geometry has been described in detail by Pershan et al 6 and can be used when the x rays FIG. 3.…”

Section: Steering Crystal Monochromatormentioning

confidence: 99%

“…Although studied for many years, fundamental questions remain concerning both the longitudinal ͑out-ofplane͒ and transverse ͑in-plane͒ structure of the interface. Recently, experimental techniques such as surface sensitive x-ray and neutron scattering [1][2][3][4][5][6][7][8][9][10][11][12][13][14] and nonlinear optical methods 15,16 have allowed these interfaces to be probed on the molecular length scale. In this article, we describe a synchrotron x-ray liquid surface spectrometer recently installed at beamline X19C at the National Synchrotron Light Source at Brookhaven National Laboratory ͑NSLS͒ and mention a few recent results from this device.…”

Section: Introductionmentioning

confidence: 99%

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A synchrotron x-ray liquid surface spectrometer

Schlossman

Synal

Guan

et al. 1997

Review of Scientific Instruments

112

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Section: Steering Crystal Monochromatormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A synchrotron x-ray liquid surface spectrometer

Schlossman

Synal

Guan

et al. 1997

Review of Scientific Instruments

112

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“…We may say that the nematic phase~the surface slightly above T[~. Similarly, the smectic phase can begin to wet the surface in the nematic phase as T tends to the nematic-smectic transition temperature and this effect has been studied by X-ray specular reflectivity techniques by Pershan, Als-Nielsen and co-workers [28], using a liquid surface reflectometer. well.…”

Section: Studiesof Fluids At Interfacesand In Thin Filmsmentioning

confidence: 99%

X-Ray and Neutron Scattering Studies of Complex Confined Fluids

Sinha

2000

Soft Condensed Matter: Configurations, Dynamics and Functionality

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. .We review recent X-ray and neutron scattering studies of the structure and dynamics of confined complex fluids. This includes the study of polymer conformations and binary fluid phase transitions in porous media using Small Angle Neutron scattering, and the use of synchrotrons radiation to study ordering and fluctuation phenomena at solid/liquid and liquid/air interfaces. Ordering of liquids near a solid surface or in confinement will be discussed, and the study, via specular and off-specular X-ray reflectivity, of capillary wave fluctuations on liquid polymer films. Finally, we shall discuss the use of highbrilliance beams from X-ray synchrotrons to study via photon correlation spectroscopy the slow dynamics of soft condensed matter systems.

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“…It has been shown that smectic layering is induced in nematic liquid crystals close to the nematic-smectic-A phase transition at the air/liquid crystal interface [3] and at solid substrates [4]. An ellipsometer uses a polarized light beam that is reflected from the surface of interest.…”

Section: Introductionmentioning

confidence: 99%

“…In the last two decades, surface-induced organisation of liquid crystals at interfaces has been an active area research using various techniques including ellipsometry [1], atomic force microscopy [2], X-ray and neutron reflectometry [3,4].…”

Section: Introductionmentioning

confidence: 99%

Surface ordering at the air–nematic interface. Part 2. A spectroscopic ellipsometry study of orientational order

et al. 2007

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* order parameter, air-nematic interface, ellipsometrySpectroscopic ellipsometry has been used to measure enhanced orientational ordering at the nematic-air interface of 8CB as the smectic-A phase was approached by cooling from the isotropic phase. The depth profile of the orientational order has been estimated by calculating the ellipsometric parameters for a homeotropic uniaxial surface film on a uniaxial subphase using the Abelès matrix method. This showed that the depth of the enhanced orientationally ordered region was ~ 10nm at 0.5°C above the nematic-smectic-A transition. This is substantially less than the thickness of the region with surface enhanced smectic order as determined by neutron reflection and a model of the surface structure consistent with both sets of results is proposed. AbstractSpectroscopic ellipsometry has been used to measure enhanced orientational ordering at the nematic-air interface of 8CB as the smectic-A phase was approached by cooling from the isotropic phase. The depth profile of the orientational order has been estimated by calculating the ellipsometric parameters for a homeotropic unaxial surface film on a uniaxial subphase using the Abelès matrix method. This showed that the depth of the enhanced orientationally ordered region was ~ 10nm at 0.5°C above the nematic-smectic-A transition. This is substantially less than the thickness of the region with surface enhanced smectic order as determined by neutron Preprint: to be published in Liquid Crystals 2 reflection and a model of the surface structure consistent with both sets of results is proposed.

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Smectic layering at the free surface of liquid crystals in the nematic phase: X-ray reflectivity

Cited by 150 publications

References 22 publications

A synchrotron x-ray liquid surface spectrometer

A synchrotron x-ray liquid surface spectrometer

X-Ray and Neutron Scattering Studies of Complex Confined Fluids

Surface ordering at the air–nematic interface. Part 2. A spectroscopic ellipsometry study of orientational order

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