Optical properties cholesteric liquid-crystal films

Optical Properties of Cholesteric Liquid-Crystal Films... 

See, for example, D. W. Berreman and T. J. Scheffer, Reflection and Transmission by Single-Domain Cholesteric Liquid Crystal Films Theory and Verification, Mol. Cryst. and Liquid Cryst, 11, p. 395 (1970) R. Dreher and G. Meier, Optical Properties of Cholesteric Liquid Crystals, Phys. Rev., A8, p. 1616(1973). 

Ma, J., Zheng, Z., Liu, Y., Xuan, L. Electro-optical properties of polymer stabilized cholesteric liquid crystal film. Chin. Phys. B 20, 024212 (2011)... 

The cholesteric mesophase is thus very widespread both in natural and in synthetic polymer systems. The capacity of synthetic polymers to retain the properties of cholesteric liquid crystals, primarily the selective reflection of circularly polarized light, in the glassy and highly elastic state, makes them promising materials for creating different optical film elements (selective filters, polaroids, reflectors, heat indicators, etc.). 

The macromolecular nature provides an interesting feature of LC polymeric cholesterics, namely the possibility of obtaining monochromic films. Thus for polymeric liquid crystals the helix pitch is practically not altered with temperature below Tg, when a cholesteric phase is frozen in a glassy matrix (Fig. 23a). This implies that fast cooling of polymeric films from a mesomorphic state (shown with arrows) fixes their optical properties, which makes it possible to use them at ordinary temperatures as selective monochromic reflectors. On the other hand, such polymeric films display the extraordinary polarizing properties of cholesterics, i.e. the different absorption... 

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