Periodic Structures in Induced Films of Tilted Smectics

Najjar, R.; Galerne, Y.

doi:10.1080/10587259908026092

Cited by 6 publications

(10 citation statements)

References 12 publications

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“…The symmetry of both systems is moreover the same: the film is sandwiched between two different media (asymmetric boundaries) and its molecules are tilted. All these common features allow one to infer that the mechanism that governs the formation of the structures presented here is essentially the same as the one discussed in ref . We therefore propose that the observed distortion is an effect of surface elasticity that favors a particular splay distortion, positive or negative, associated with a slight tilt modulation.…”

Section: Resultssupporting

confidence: 70%

“…The effect is clearly seen in Figure 7, with the intensity of every second maximum being larger. The distortion is therefore analogous to the one discussed in surface-induced films: 9,10 it corresponds similarly to a continuous rotation of the director. More significantly, it also appears spontaneously, which indicates that the energy of the distorted film is surprisingly lower than that of the uniform state.…”

Section: Resultsmentioning

confidence: 52%

“…We therefore propose that the observed distortion is an effect of surface elasticity that favors a particular splay distortion, positive or negative, associated with a slight tilt modulation. When the associated surface elastic constant K 1 (as defined in ref ) reaches a threshold value, the continuous distortion of c⃗ becomes energetically favorable. In other words and in a very simplified way, one may say that the molecules have some natural tendency not to stay parallel to each other but rather to slightly diverge.…”

Section: Resultsmentioning

confidence: 99%

“…Mesogens are of particular interest because of their ability to form freely suspended films with thickness ranging from two to hundreds of layers, or supported films on various substrates, either solid or liquid. This latter category includes surface-induced films, where the surface freezing effect induces smectic layers at the surface of an isotropic droplet of the same material, − and the so-called hybrid films, which are much thicker (∼micrometers) and form when a drop of nematic liquid crystal is placed on a glycerol surface . Another simple way for preparing and studying thin films is to use the Langmuir−Blodgett technique (LB), as mesogenic molecules very often display amphiphilicity .…”

Section: Introductionmentioning

confidence: 99%

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Organization of a Polar Molecule at the Air−Water Interface

et al. 2004

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We have studied the behavior of a low molecular mass organosiloxane ferroelectric liquid crystal at the air−water interface. Data obtained with Langmuir isotherms, surface potential measurements, and Brewster angle microscopy are presented and discussed. The compound forms films on the Langmuir trough, with phase transitions to multilayers upon compression. As seen with Brewster angle microscopy, the monolayers are optically isotropic whereas striking birefringent structures develop in the multilayer films. These periodic structures result from a surface elasticity phenomenon.

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Section: Resultssupporting

confidence: 70%

Section: Resultsmentioning

confidence: 52%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Organization of a Polar Molecule at the Air−Water Interface

et al. 2004

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“…"Swimming" smectic surface layers on isotropic liquid droplets have been observed at temperatures above the clearing point (see e.g. [72][73][74]). Likewise, solid substrates may induce orientational ordering at temperatures above the bulk clearing point (see e.g.…”

Section: Introductionmentioning

confidence: 98%

Surfaces and Interfaces of Free-Standing Smectic Films

Schüring¹,

Stannarius²

2004

Molecules in Interaction With Surfaces and Interfaces

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Abstract. Free-standing smectic films are unique fluid objects with an exceptionally large surface-to-volume ratio. They are excellently suited for studies of surface and interface properties of liquids. We describe surface tension measurements in the smectic and isotropic phases, with particular emphasis on anomalies near the phase transitions. A model that considers the excess surface entropy of ordered surface layers is applied to describe the experimental observations qualitatively and quantitatively. From the geometrical properties of isotropic droplets in free-standing films and from the forces acting on these droplets, interface tensions between the smectic and isotropic phases are derived. Finally, we report measurements of the gas permeation through smectic films and develop a model for the description of the film-thickness dependence of the permeation coefficient.

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2-Dimensional Elastic Constant in Asymmetric Films of Tilted Smectics

Najjar

Galerne

2001

Molecular Crystals and Liquid Crystals Science and Technology.

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We report on what we believe to be the first measurement of the surface elastic constant, K,. This new elastic constant is manifested through the formation of a purely elastic instability. The instability is observed to form in thin smectic films, which are induced at the free surface of a liquid crystal droplet. Under polarising microscope, the instability is viewed as an array of interference fringes, which denote variation of both the orientation and the amplitude of the c director. The instability corresponds to a continuous rotation of the c director coupled to modulations of the molecular tilt angle 8. We propose that this mechanical instability is produced by the surface elastic term, Klc2divc. This new term to consider in the free energy density is found to be consistent both qualitatively and quantitatively with the experiments.

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Periodic Structures in Induced Films of Tilted Smectics

Cited by 6 publications

References 12 publications

Organization of a Polar Molecule at the Air−Water Interface

Organization of a Polar Molecule at the Air−Water Interface

Surfaces and Interfaces of Free-Standing Smectic Films

2-Dimensional Elastic Constant in Asymmetric Films of Tilted Smectics

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