Structures dichroic dyes

Other schemes involving dichroic dyes with heat and electrical fields are also possible. Each of the possibilities could use the plastic structure of the substrates, its durability, or both. This approach would recycle the material for carrying the printed messages at the point of use, eliminating handling and distribution costs, and would require a fraction of the enormous amount of paper now consumed in delivering news and other literary material. The newspaper or periodical would have the familiar size and appearance and would present little change to the reader. The convenience of real on time home delivery and other built in aspects of the system would make it a useful successor to the present one. (This is just a point to discuss and amuse oneself but it could happen.)... 

Figure 2. Schematic structure of side chain liquid crystal polymers with dichroic dyes (imparting nonlinear optical properties) and mesogenic side groups.

Table 3.19 Molecular structure, peak absorption (k ax .abs nm), colour and order parameter for the dichroic dyes (156-165)...

A suitable surface treatment results in a homeotropic orientation for a nematic mixture incorporating a dichroic dye of positive contrast and an amount of a chiral dopant insufficient to overcome the surface forces and generate a twisted structure in the nematic phase. 

Absorbing systems circular dichroism When linearly dichroic dye molecules are dissolved in a cholesteric liquid crystal the medium exhibits circular dichroism because of the helical arrangement of the solute molecules in the structure. The theory developed above can be extended to take into account the effect of absorption by treating the layers as both linearly birefringent and linearly dichroic. Assuming that the principal axes of linear birefringence and linear dichroism are the same, the Jones matrix of any layer with reference to its principal axes is... 

When a polarized spectrum of the film was taken in the dry state, a small dichroic ratio was observed (A L/A// = 1.3, see Fig. 9c). This is due to the slant structures of base pairs and intercalated dyes to the axis of the strands, since the DNA strands were confirmed to be aligned along the stretching direction even in the dry film (see Fig. 7c). These changes of polarized absorption spectra dependent on water moisture were reversible at least 10 times. 

Linear-dichroic spectra of SA monolayers prepared from mixtures of OTS and a cyanine-dye surfactant established the absence of dimerization and the orientation of the chromophore parallel to the substrate [183]. In contrast, the same cyanine dye underwent sandwich-type dimer formation in LB films and had its chromophore oriented perpendicular to the water surface [192]. These results highlight an important difference between LB and SA monolayers. Parameters which determine monolayer formation on an aqueous subphase are also responsible for the orientation and organization of the surfactants therein. Furthermore, the configuration of the surfactants is retained regardless of the structure of the substrate to which the floating monolayer was subsequently transferred to by the LB technique. Conversely, in SA monolayers, surfactant organization is primarily dependent upon the nature of the substrate [183]. 

Molecular structure and absorption spectrum of an organic dye with a positive dichroic ratio. 

Similar lifetime issues were encountered for a large variety of dyes with an elongated molecular structure with an extended conjugated core similar to that of the azo dyes, such as the merocyanine dyes (163-165 n = 1-3), shown in Table 3.19, as well as azomethines and methine dyes. However, most of these exhibit much lower order parameters and dichroic ratios than conventional azo dyes prepared earlier. 

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