Optical guest-host effect

Stahelin, M., Walsh, C. A., Borland, D. M., Miller, R. D., Twieg, R. J., and Volksen, W. Orientational decay in poled 2nd-order nonlinear-optical guest-host polymers Temperature dependence and effects of poling geometry. J. Appl. Phys. vol. 73 (no. 12), 15 [une 1993, p. 8471-8479. 

The electro-optical measurements were carried out using an electro-optical cell described by Talroze, et al. which was mounted on a heating stage of a polarizing microscope, MIN-8. A photo-element was used in conjunction with a recorder to monitor the transmitted light intensity. The film thickness was about 12 pm, electric field intensity was 10 V/cm. The pleochroic dye for studying the guest host effect had an absorption band at 505 nm. 

Incorporation of a pleiochroic dye and elimination of the analyzer results in voltage-controlled optical absorption, the guest-host effect. ... 

The results of studying the optical properties (birefringence, IR and UV dichroism), x-ray, spectroscopy, NMR, and EPR (with specially introduced paramagnetic probes) methods are usually used for estimating the order parameter [40]. The so-called guest-host effect is a widely used method (cf. Chapter 8). 

The use of the guest-host effect not only permits controlling the optical properties of dyed polymer films but also makes it possible to measure the S order parameters of the liquid crystal. Measurement of the order paramet is usually done by either analyzing the dichroic ratio of plane-orient films with... 

The guest host effect realized in polymers on addition of a dichroic dye and untwisting of the cholesteric helix open up certain prospects for the construction of solid optical elements based on LC polymers such as dichroic polaroids and selective filters. The important possibility of obtaining ferroelectric polymeric LC materials was recently demonstrated in [67]. 

The question that emerges at the climax of this survey relates to the possibility of using crystalline inclusion phenomena for optical resolutions of molecular species. Can this be done effectively with suitably designed host compounds The definitely positive answer to this question has elegantly been demonstrated by Toda 20) as well as by other investigators (see Ch. 2 of Vol. 140). An optically active host compound will always form a chiral lattice. Therefore, when an inclusion type structure is induced, one enantiomer of the guest moiety should be included selectively within the asymmetric environment. 

Kaino and co-workers [255] have investigated the effect of polymer polydis-persity on electro-optic materials properties. No dependence on polydispersity was observed for guest host materials but for Disperse Red chromophores covalently attached to monodisperse polystyrene weaker absorption tails were observed. This result suggests that chromophore-chromophore interactions are modified by the polymer host. 

Analysis of the electro-optical characteristics of GH-LCDs showed that for all types of guest-host chiral nematic phase change effects the contrast is greatest when... 

On the other hand, liquid crystalline polymers applied to optical information storage has attracted great attention. The liquid crystalline polymer is applied mainly in terms of the thermo-optical effect. The backbone of liquid crystalline polymer can be polysiloxane, polyacrylate, or polyesters. In order to enhance the absorption coefficient for the writing laser beam, the dyes may be either dissolved into the liquid crystalline polymer in the guest-host model or attached to the backbone of the liquid crystalline polymer to form a copolymer. The nematic, cholesteric and smectic liquid crystalline polymers are all be able to be utilized in optical information storage. 

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