Gel-glass dispersed liquid crystals

Figure 1.20 Encapsulation of microdroplets of liquid crystals in ORMOSIL matrices results in materials with better transparency and thermal stability than polymer-dispersed liquid crystals. Gel-glass dispersed liquid crystal device switched between the OFF and ON state (thickness 10 pm, 4 x 2 cm, Fp p = 90V). (Reproduced from ref. 45, with permission.)...

Gel-Glass-Dispersed Liquid Crystal (GDLC) Materials... 

Zayat, M. and Levy, D. (2003) Surface organic modifications and the performance of sol—gel derived gel—glass dispersed liquid crystals (GDLCs). Chem. Mater., 15, 2122 2128. 

Chang, W.P., Whang, W.T., and Wong, J.C. 1995. Electrooptic characteristics of amino-gel-glass-dispersed liquid-crystal and its matrix formation. Jpn. J. Appl. Phys. 34(4A) 1888-1894. 

Chapter 20 Electro-Optical Properties of Gel-Glass Dispersed Liquid Crystals... 

There are three combinations of the two components of nematic network gels (1) an isotropic network swollen by a nematic solvent, reminiscent of the polymer dispersed liquid crystal systems (PDLC). This case (1) was discussed by Brochard (1979) and Ballauff (1991) (2) a nematic network swollen by an isotropic solvent was actually studied experimentally by Carudo et al. (1992) and theoretically by Warner and Wang (1992a) (3) both components can order at a temperature above the glass transition. Actually the first two systems are special cases of the last one which has been experimentally investigated (Zentel, 1986 Barnes et al., 1989 Kishi et al., 1994) and theoretically studied (Wang Warner, 1997). 

The continuous phase can be a solid or have some characteristics of a solid. This implies that the structural elements are immobilized, which considerably enhances physical stability of the system. When making such a dispersion, the continuous phase is always liquid, but it can solidify afterwards, e.g., by lowering the temperature or by evaporating the solvent. The liquid can become crystallized, form a glass (Section 16.1), or turn into a gel. Especially the last named situation is frequently encountered in foods. Also the solvent, generally an aqueous solution, in the continuous phase then is more or less immobilized (Section 5.3). If the gel is a classical polymer gel (Section 17.2.2), the polymer molecules provide a continuous network, but do not make up a continuous phase the polymer strands cannot be seen as a structure in which other molecules can be present and diffuse. 

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