Bipolar droplet

Note 3 A bipolar droplet texture occurs when the director lies in the plane of a nematic-isotropic interface. 

Figure 11.15 Liquid crystal director configurations confined in droplets in PDLCs (a) bipolar droplet, (b) toriodal droplet, (c) radial droplet, and (d) axial droplet.

In the bipolar droplet, the rotation symmetry axis is referred to as the bipolar axis. The droplet... 

Figure 11.16 Microphotographs of PDLCs (a) bipolar droplets, (h) radial droplets.

Besides the four droplet configurations discussed above, other droplet configurations could exist under appropriate conditions. For example, there is a twisted bipolar droplet where the splay and bend elastic energy is reduced by introducing twist deformation. The point defect in the radial droplet could escape away from the center in an effort to reduce the total free energy. 

Calculate the director configuration inside a bipolar droplet with the radius R = 5 pm R... 

Figure 5. NMR spectra of the radial left) and bipolar droplet right) for different values of the diffusion parameter A A = 0 corresponds to the no-diffusion limit, while A = 32 corresponds to the fest diffusion limit. Radial droplet The Pake-type powder spectrum obtained for A = 0 collapses into a single line centered at zero quadrupolar splitting for A = 32. Bipolar droplet The mckgnetic field is aligned along the bipolar symmetry ajds, which results in a spectrum consisting of two lines both in absence of diffusion and in the fest diffusion limit.

Figure 8. H NMR spectra of the bipolar droplet in the nematic phase at T = 0.8 for different values of the external field strength (oc y/rj) no-diffusion limit (a), fi t diffusion Umit (b). The quadrupolar splitting increases with increasing t). All spectra have been normalized so as to obtain same peak heights.

Considering now Fig. 8 (b) and the spectra of bipolar droplets in the fast translational diffusion limit (or, equivalently, in small enough nematic droplets), the spectra for all 77 still consist of two well-defined lines now positioned, however, at an average quadrupolar frequency given by... 

Figure 9. Order parameters calculated for the bipolar droplet at T = 0.8 (nematic phase) local nematic (5, left) and external field ((P2)b, right) order parameter as a function of the distance from the droplet center. Curves are plotted for (top to bottom) = 1, 0.5, 0.2, and 0, respectively. External field enhances the degree of nematic ordering (left) and increases the size of the aligned core (right). The molecular alignment for = 0 is depicted schematically as inset.

Figure 10. Spectra of 1000 bipolar droplets at T = 0.8, with symmetry axes oriented randomly no diffusion (a), fast diffusion inhomogeneous (b) and homogeneous (c).

The director field in a bipolar droplet of a liquid crystal, found, for example, in a polymer-dispersed liquid crystal (Fig. 5.30), can be written as a function of the polar angle... 

The minimum value of voltage above which transmittance saturates is termed as saturation voltage (Von) (Blinov and Cigrinov 1994 Drzaic 1995 Deshmukh and Jain 2014). Wu et al. (1987) gave the mathematical formulae of threshold and saturation voltage (for bipolar droplet) by the balance between the elastic force, surface interaction and applied electric force and is estimated as (Kalkar et al. 2008 Ahmad et al. 2012b) ... 

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