Nematic droplet

Doane J W 1986 Field controlled light scattering from nematic micro droplets App/. Phys. Lett. 48 269-71... 

J. Dzubiella, M. Schmidt, H. Lowen. Microstructure of topological defects in nematic droplets (submitted). 

Lyotropic liquid crystalline nanoparticles have also been described. Concentrated solutions of gold nanorods in water in the presence of a surfactant (cetyltrimethyl-ammonium bromide) display a nematic mesophase stable up to 200 °C [74[. The N mesophase was identified by optical microscopy by their typical nematic droplets texture. 

To produce novel LC phase behavior and properties, a variety of polymer/LC composites have been developed. These include systems which employ liquid crystal polymers (5), phase separation of LC droplets in polymer dispersed liquid crystals (PDLCs) (4), incorporating both nematic (5,6) and ferroelectric liquid crystals (6-10). Polymer/LC gels have also been studied which are formed by the polymerization of small amounts of monomer solutes in a liquid crystalline solvent (11). The polymer/LC gel systems are of particular interest, rendering bistable chiral nematic devices (12) and polymer stabilized ferroelectric liquid crystals (PSFLCs) (1,13), which combine fast electro-optic response (14) with the increased mechanical stabilization imparted by the polymer (75). 

Many other interesting examples of spontaneous reflection symmetry breaking in macroscopic domains, driven by boundary conditions, have been described in LC systems. For example, it is well known that in polymer disperse LCs, where the LC sample is confined in small spherical droplets, chiral director structures are often observed, driven by minimization of surface and bulk elastic free energies.24 We have reported chiral domain structures, and indeed chiral electro-optic behavior, in cylindrical nematic domains surrounded by isotropic liquid (the molecules were achiral).25... 

Spherical droplet that forms during a transition from an isotropic phase to a nematic mesophase. It has characteristic textures that depend on the droplet size and the director orientation at the nematic-isotropic interface. 

Note Nematic droplets display a texture characteristic of a nematic mesophase since they occur nowhere else. 

Texture with two point defects at the poles of a nematic droplet. 

Note 3 A bipolar droplet texture occurs when the director lies in the plane of a nematic-isotropic interface. 

Texture with one point defect at the center of a nematic droplet. 

Polymer-dispersed liquid crystals (PDLCs) are made up of nematic liquid crystals dispersed in a solid continuous polymer matrix. These are prepared by mixing a reactive monomer into a non-polymerisable LC medium and then polymerising the reactive monomer to create a polymer matrix, at the same time capturing the LCs as dispersed droplets, greater than 1 pm in diameter, i.e. the wavelength of visible light.3 -33... 

It can be safely predicted that applications of liquid crystals will expand in the future to more and more sophisticated areas of electronics. Potential applications of ferroelectric liquid crystals (e.g. fast shutters, complex multiplexed displays) are particularly exciting. The only LC that can show ferroelectric property is the chiral smectic C. Viable ferroelectric displays have however not yet materialized. Antifer-roelectric phases may also have good potential in display applications. Supertwisted nematic displays of twist artgles of around 240° and materials with low viscosity which respond relatively fast, have found considerable application. Another development is the polymer dispersed liquid crystal display in which small nematic droplets ( 2 gm in diameter) are formed in a polymer matrix. Liquid crystalline elastomers with novel physical properties would have many applications. 

Fig. 8 (a) Schematic representation of the structure of the chiral nematic phase of DNA, showing continuously twisting nematic layers, giving rise to a p/2 periodicity easily observable in the side view on the left, (b) N droplets observed in polarized microscopy. The bright and dark stripes correspond to p/2 (size bar is 10 pm). Adapted with permission from [27]... 

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