Alignment planar

Note 2 Sometimes a uniform planar alignment is called a uniform homogeneous alignment . The latter term is not recommended. 

Molecular alignment for which the director rotates in a helical fashion when passing between two substrate surfaces having molecules in uniform planar alignments. 

Note 3 Schlieren textures observed in nematic samples with planar alignment show defect centers with two or four emerging brushes. Schlieren textures in nematic samples with tilted alignments show centers with four brushes centers with two brushes are caused by defect walls. 

Regions in a liquid crystal having a specific cellular periodic flow-pattern in the form of long rolls induced by the application of an electric field perpendicular to a nematic layer with an initial planar alignment of the director. 

Tuning of the pre-tilt angle at the interface was also demonstrated by doping commonly used polyimide alignment layers with POSS nanoparticles [339]. In addition, the fabrication of a tunable liquid crystal flat microlens was achieved by placing a drop of a nematic liquid crystal doped with POSS nanoparticles onto a substrate inducing planar alignment (local HAN mode) [340]. Simultaneously, Takatoh and co-workers extended this concept to a series of metal oxide... 

Recently, Chen and co-workers also presented a combination of photo- and nanoparticle-induced alignment, where the homeotropic alignment induced by POSS nanoparticles can be changed into planar alignment by adsorption of a photo-excited azo-dye [346-348]. 

The electrode surfaces of a normal LCD sandwich cell d 8-10 pm) are coated with an alignment layer in order to induce a planar alignment of a host (chiral) nematic mixture containing the dichroic dye of positive dichroism and a chiral dopant. Due to the absence of polarisers a very thin mirror can be incorporated within the cell on top of the rear glass plate electrode in direct contact with the guest-host mixture, see Figure 3.15. 

Cell Construction. The optical interference technique to be used here is a modification of that described by Gramsbergen and de Jeu. This method uses a thin paraUel-plate cell containing a planar aligned nematic liquid crystal sample. The sample cell consists of two parallel 15 X 50 mm microscope slides separated by a gap D in the range 50-100 /zm, which is determined by spacer shims. A description of its construction is given below. 

Petschek [4] used heterocyclic rigid-rod polyionomers, including poly(pyr-idinium) salt, (III), and poly(benzimidazole-sulfonate), (IV), for coating directionally onto charged surfaces to impart planar alignment and pre-tilt to the surfaces. 

The Optical-Induced Freedericksz Transition of Nematic Liquid Crystal (5CB) doped with l%(w/w) of 5, 10, 15, 20-tetraphenylporphyrinatozinc( II) (ZnTPP) were studied. Excited by Ti Sappire laser with the 82MHz repetition rate and lOOfs pulse duration, the optical Freedericksz threshold of a 23.6pm-thickness planar alignment sample occurred at an intensity level of0.35mW/mm in contrast to the normally observed 83mW/mm value for pure 5CB. The coordination-bonding interaction between 5CB and ZnTPP were discussed by UV-vis and fluorescence spectra. We attribute the reduction of the optical Freedericksz threshold to the coordination-bonding interaction. 

ZnTPP was synthesized in our laboratory and characterized by UV-vis, EA, H-NMR, IR, MS and 5CB was from BDH (as shown in Figure 1). Two samples were studied in the experiment, 5CB and 5Cb doped with 1% (w/w) ZnTPP. The samples were sandwiched between two glass substrates with 23.6pm spacers, the two glass substrates were coated with polyimide and rubbed unidirectionally to give planar alignment. 

Figure 3. Light transmission T vs. light intensity I for planar alignment 5CB doped with 1% ZnTPP.

Inspection of the data of Figure 5 and assuming that and are correct, i.e. that the U and P samples are fully unaligned and fully planarly-aligned, shows that Cn (calc) should be near 14.5 whereas the experimental value for 12 - 12.5. This indicates that the... 

Fukuda, K., Seki, T., Ichimura, K., and Komitov, L. Uniform planar alignment of nematics on photooriented linear polysilane. Mol. Cryst. Liq. Crys., 368, 535 (2001). 

B). Although facial differentiation would not be feasible in this case due to the planar alignment, the Lewis acid will be syn or anti to particular substituents (R ). The third, a bent non-planar mode of bonding results from movement of the metal out of the carbonyl n nodal plane (C), which is often adopted by the bulky Lewis acids. The last mode is a coordination of metal to the C=0 n bond, where the carbonyl is formally the donor, but back-bonding into the C=0 n orbital occurs (D), This mode has been reported for transition metal complexes [5J. The metal center is... 

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