Search results for "Liquid Crystal"

Long working range light field microscope with fast scanning multifocal liquid crystal microlens array

2018

The light field microscope has the potential of recording the 3D information of biological specimens in real time with a conventional light source. To further extend the depth of field to broaden its applications, in this paper, we proposed a multifocal high-resistance liquid crystal microlens array instead of the fixed microlens array. The developed multifocal liquid crystal microlens array can provide high quality point spread function in multiple focal lengths. By adjusting the focal length of the liquid crystal microlens array sequentially, the total working range of the light field microscope can be much extended. Furthermore, in our proposed system, the intermediate image was placed i…

Ferroelectric Liquid Crystalline Elastomers

2002

Ferroelectric LC-elastomers represent an interesting class of material because they combine the ordering of liquid crystalline ferroelectric phases and the rubber elasticity of polymer networks. Switching of the electric polarization leads to deformation of the polymer network, equivalent to stretching a spring, and creates a stress in the network of polymer chains. The interaction of mesogens and the network can be varied by using different topologies of net points: Crosslinking is carried out either within the siloxane sublayers (leading to fast switching elastomers) or between the siloxane sublayers (resulting in an elastomer that favors the ferroelectric switching state in which the cro…

Director orientation in chevron surface-stabilized ferroelectric liquid crystal cells. Verification of orientational binding at the chevron interface…

1990

Abstract We present results of theoretical modelling and experimental study of director distributions and the associated optical properties of chevron surface stabilized ferroelectric liquid crystal (SSFLC) cells. Chevron cells are modelled as being two stacked FLC slabs, described by distinct orientation distributions of the director [ncirc]-polarization P([ncirc] – P) couple. In each slab the [ncirc] – P distribution is governed by bulk Frank elastic and electric field-induced torques and by surface torques at the FLC-solid interface and at the chevron interface, where the two distributions are coupled. The optical properties of such structures are calculated numerically and the results t…

Thermotropic polyesters with mesogenic groups based on substituted hydroquinone units and highly flexible siloxan spacer in the main chain

1984

New thermotropic Polyesters having mesogenic groups based on substituted hydroquinone units and highly flexible oligosiloxan spacer in the main chain, are synthesized and characterized. The mesophase formed at low temperature are studied by differential scanning calorimetry (DSC) and polarized light microscopy. The liquid crystalline behaviour of these polyesters, particulary their transition temperatures and the mesophase width could be explained on the basis of their structural features.

1991

It is shown that the acceptor polyesters [(CH 2 ) x OCOC(=R) COO(CH 2 ) x ] n (R=9-[2,4,7-trinitrofluorenylidene]) x=3, 6, 8) influence the chain behaviour of the discotic hexapentyloxytriphenylene without changing the phase type (D ho ). The clearing temperature of the complexes has a maximum value when x=G. Both intra- and intercolumnar distance are smaller than in the pure discotic compound and independant of the spacer

Electric Field Effects and Miscibility in Cybotactic Micellar Nematic and Ordinary Nematic Polyesters

1984

Abstract Miscibility behavior and electro-optical instabilities are reported for two main chain thermotropic nematic polyesters formed by regularly alternating a disubstituted azoxy-benzene mesogen with a flexible spacer containing either 7 or 10 methylene units (HEPTA-9 and DDA-9, respectively). Polymer HEPTA-9 displays an ordinary nematic organization and polymer DDA-9 forms a cybotactic nematic phase. Both are totally miscible with each other, and with PAA, in the nematic phase. Williams domains and dynamic scattering modes are observed in both cases.

Electro-Hydrodynamic Instabilities in Main Chain Thermotropic Liquid Crystalline Polyesters

1984

Abstract We have investigated the response behavior of the thermotropic nematic polymer, DDA-9, in an electric field. DDA-9 is composed of regularly alternating moieties and flexible spacers. At a critical threshold voltage, dependent on molar mass, these polymers show the onset of instability. The appearance of a (non-fluctuating) striped pattern (Williams domains) is shown and the time of formation and relaxation of these patterns is investigated as a function of applied Voltage.

1986

Influence des groupes mesogenes sur le polymorphisme de polyphenylene-1,4 terephtalate et differents polyesters a chaine principale semi-flexible

1992

The synthesis of a new type of combined polymers containing both disc- and rod-like mesogens is reported. The polyesters, having a triphenylene derivative as a discotic mesogen in the side group and azobenzene or biphenyl derivatives as rod-like mesogens in the main chain were characterized by polarizing microscopy, differential scanning calorimetry, and X-ray scattering studies. The homopolymer 7 is highly crystalline, while the copolymer 8 is amorphous, both, however, do not form liquid-crystalline phases.

Monolayers of rod-shaped and disc-shaped liquid crystalline compounds at the air-water interface

2008

Calamitic (rod-shaped) and discotic (disc-shaped) thermotropic liquid crystalline (LC) compounds were spread at the air-water interface, and their ability to form monolayers was studied. The calamitic LCs investigated were found to form monolayers which behave analogously to conventional amphiphiles such as fatty acids. The spreading of the discotic LCs produced monolayers as well, but with a behaviour different from classical amphiphiles. The areas occupied per molecule are too small to allow the contact of all hydrophilic groups with the water surface and the packing of all hydrophobic chains. Various molecular arrangements of the discotics at the water surface to fit the spreading data a…