Polymer Dispersed Liquid Crystals PDLC

There are three principal methods of fabricating PDLC (to disperse liquid crystals in polymer matrix) phase separation, encapsulation and permeation. In the phase separation method, liquid crystal materials, prepoljnner (monomer or oligomer) and photoinitiator (curing agent) are mixed, and then polymerization is brought about by heating [2] or UV irradiation [3]. During the polymerization, the liquid crystal material phase separates from the solution, and liquid crystal droplets and a polymer matrix are formed. By measurement of the nematic-isotropic transition temperature, the purity of the liquid crystal in the droplets can be checked. In the case that the polymerization-induced phase separation is not complete and unreacted prepolymer is dissolved in the liquid crystal droplets, the 

Encapsulation [4] is brought about by emulsifying a liquid crystal in a waterborne polymer such as polyvinyl alcohol (PVA) the emulsion is then coated on a substrate and dried. The permeation method [5] is used for basic studies and the liquid crystals are permeated into the pores of a prefabricated polymer matrix. 

5 Vertical Alignment (VA) Mode and Multi-domain Vertical Alignment (MVA) Mode 

1 Layer Structure and Molecular Orientation of Ferroelectric Liquid Crystals 

At first in this chapter, ferroelectric liquid crystals (FLCs) and their most interesting application as surface stabilized ferroelectric liquid crystals (SSFLCs) are briefly explained. 

O 2005 Kohki Takatoh, Masald Hasegawa, Mitsuhiro Koden, Nobuyuki Itoh, Ray Hasegawa and Masanoii Sakamoto 

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C2.2.4.5 POLYMER DISPERSED LIQUID CRYSTAL (PDLC) DISPLAYS... 

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). 

Refraction of light Polymer dispersed liquid crystals (PDLC), gel and polymer network displays... 

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... 

ICP thin films were used as driving electrodes for polymer-Dispersed Liquid-Crystals (PDLC) display devices. Liquid-crystalline-based display devices, which are commonly made of a liquid-crystal compound sandwiched between two substrates coated with a conducting layer of indium tin oxide (ITO), whose substitution with ICP electrodes could improve the optical and mechanical properties of the display devices. On the way to all-organic displays, PDLC sandwiched between two plastic substrates coated with ICP layers are promising devices for paper-like displays for electronic books which require flexibility, lightness, and low-power consumption. The electro-optical characteristics (transmission properties, drive voltages and switching times) of the PDLC devices depend on the nature of the ICP substrate used [13]. 

To form cholesteric liquid crystalline polymers, one either polymerizes cholesteric monomers or mixes low molecular mass cholesteric liquid crystals with polymers. In the latter case, two components may be mixed homogeneously or in such a way that the polymers act as a matrix while the small molecular mass cholesteric liquid crystals are in droplets, known as the polymer-dispersed liquid crystals (PDLC) (Doane et al., 1988) or the nematic curvilinear aligned phase (NCAP) (Fergason, 1985). In addition, there are many polymers in nature exhibiting the cholesteric phase such as PBLG, cellulose, DNA, etc. 

The sensitivity of deuteron NMR to the molecular orientational order and to director field configurations turned out to be extremely useful in studies of liquid crystals confined into snbmicrometer pores. Moreover, the large surface-to-volume ratio of these composite systems render the interfacial and surface phenomena, induced by the liquid crystal-surface interactions, accessible even to an essentially integrative technique like NMR. Since the discovery of polymer dispersed liquid crystals (PDLCs) in 1986 [4], NMR of selectively deuterated liquid crystals was used to discriminate unambiguously among various director structures in cavities, resulting from an interplay between elastic forces, morphology and size of the cavity, and surface interactions. These structures include the escaped-radial, planar axial, planar-polar, and... 

Novel, flexible, completely organic, polymer dispersed liquid crystal (PDLC) "light valves" were fabricated using two flat pieces of commercial overhead transparency substrates (Nashua j -20) coated with polypyrrole between which a film of commercial PDLC material (Norland Products Co. NOA 65 optical adhesive and BDH Ltd. E7 liquid crystal fluid together with EM. Ind. 15 micron polystyrene spacers) was sandwiched. The optical adhesive was polymerized by exposure to UV light. Thin conducting polypyrrole films of varying controllable thickness were deposited on the overhead transparency. 

In polymer dispersed liquid crystals (PDLCs), the concentrations of polymer and liquid crystal are comparable. Liquid crystals form isolated droplets embedded in polymers. We will consider first the liquid crystal director configuration inside droplets, and then the electro-optical properties of PDLCs, as weU as their applications. 

H. J. Comelissen, J. H. M. Neijzen, F. A. M. A. Paulissen, and J. M. Schlangen, Reflective direct-view LCDs using polymer dispersed liquid crystal (PDLC) and dielectric reflectors, Proc. Inti. Display Research Conf. 97, 144 (1997). 

Polymer Dispersed Liquid Crystals (PDLCs) are widely researched materials of commercial importance in the electro-optical device industry as their light transmission can be changed by the application of an electric field. The refractive index of these rod-shaped liquid crystals along and perpendicular to their major axis is... 

Polymer-dispersed liquid crystals (PDLC) [7] are materials that consist of microscopic nematic droplets, with typical radii from a few hundred Angstrom to more than a micron, embedded in a polymer matrix (see Fig. 1). These systems are interesting both for technical applications and for an understanding of the behavior of mesophases in a confined environment. PDLC droplets also represent practical realizations of systems exhibiting topological defects of interest in many fields... 

Polymer-dispersed liquid crystals (PDLCs) are pm-sized dispersions of nematic liquid-crystalline droplets within a polymeric matrix (1-3). They are finding intense interest for applications such as light switches in flat-panel displays and windows (3, 4). They are usually prepared by UV-induced phase separation and cross-linking of a prepolymer containing a compatible blend of liquid crystals (LCs), although solution-casting from a common solvent and cooling from the melt below the upper-critical-... 

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