Molecular orientation pretilt angle

Fig. 6.14. Ion beam incidence angular dependence of the liquid crystal pretilt angle (3 and the molecular tilt angle 7 of the polymer segment distribution at the film surface for polyimide (top) and amorphous carbon (bottom). As predicted by the alignment model the liquid crystal pretilt angle / follows the molecular tilt angle 7. The line is a fit to y 0) using a model that assumes finite, but different cross sections for breaking of phenyl rings oriented along or perpendicular to the ion beam direction [35].

Fig. 6.10. (A) Liquid crystals align on rubbed and ion beam irradiated polyimide surfaces along the treatment direction, but with opposite pretilt angles. (B) The respective polarization dependences possess the same overall orientation, but opposite shifts with respect to a = 0° within the plane parallel to the rubbing direction (solid squares). This is in agreement with the presented alignment model, as the derived molecular distribution factors illustrate (C).

The molecular orientational states of SSFLCs are classified by the optical viewing conditions and the relationship between the directions of bend of the layer structure and the surface pretilt angle. The molecular orientational models of the states have been considered and illustrated with regard to the experimental results, and useful information has been obtained from optical simulations using the models. The influence of the surface pretilt angle on the orientational and the optical properties of SSFLCs has been described. 

The molecular orientational states of the SSFLCs have been analyzed by polarizing microspectroscopy and optical simulation. The X-ray studies indicated that the chevron layer structure is determined by the bulk properties of the FLC, but the molecular orientation in the smectic layer is strongly influenced by the surface properties. The effect of surface pretilt angle on the molecular orientation and the optical properties of SSFLCs have been studied by the optical simulation based on the molecular orientational models. 

Table 5.1.3 Baking temperatures sind pretilt angles of aligning films used for molecular orientational study... 

Molecular orientational models CIU, CIT, C2U and C2T and the high pretilt angle C2U states are shown in Fig. 5.1.20. The molecules are almost uniformly tilted to one side from the layer normal in both the CIU and C2U models. The... 

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