Azimuthal anchoring energy

Measurements of the LC azimuthal anchoring energy coefficient W(f oi the PVCN substrates (Fig. 5.9) were performed by preparing twist cells with... 

For consistency we go back to the problem of the twisted cell discussed in Section 8.3.2, however, the director angles cp at the boundaries will be not constant but can be changed due to elastic and external torques. Let a nematic layer be confined by two plane surfaces with coordinates zj = —plane through angle cp (there is no tilt, the angle 9 = ti/2 everywhere, and the azimuthal anchoring energy is finite). 

In the Rapini approximation, the zenithal and azimuthal anchoring energies are defined for the director n in terms of angles a and p ... 

Only few data are available for other liquid crystal phases (apart from nematics). For example, the azimuthal anchoring energy was recently measured in the ferroelectric smectic C phase [75]. 

Such a multistable orientation was observed when a capillary was formed by two mica (sixfold symmetry, three easy directions) or NaCl (fourfold symmetry, two easy directions) plates [80, 81]. The director can be switched from one equilibrium position to the other by an electric field (the azimuthal anchoring energy for 5CB between NaCl substrates was shown to be of the order of 10 erg-cm [80]. 

Fig. 2.3 Receding water contact angles on polyimide and the azimuthal anchoring energy in LC cells as a function of the number of rubbings and the pile impression. Reproduced by permission from [62].

Fig. 2.24 Azimuthal anchoring energy as a function of the groove frequency. Calculated based on the elastic energy.

Fig. 3.18 Relation between UV dosage and azimuthal anchoring energy.

Fig. 2.38 Relation between azimuthal anchoring energy and actual twist angle of a 90° TN cell.

Obi M, Morino S, Ichimura K (1999) Factors affecting photoalignment of liquid oystals induced by polymethacrylates with coumaiin side chains. Chem Mater 11 656-664 Oku bo K, Kimura M, Akahane T (2003) Measurement of genuine azimuthal anchoring energy in consideration of liquid crystal molecular adsorption on aligmncait film. Jpn J Appl Phys 42 6428-6433... 

The azimuthal anchoring energy can be measured using a substrate with a rubbed PI alignment layer and that with a photoaligned layer assembled with a twisted nematic configuration [35] (Figure 3.12). 

Figure 3.13 LC polar and azimuthal anchoring energy as a function of the thickness of the SDl photoahgning layer [39]. Reproduced from Vladimir Chigrinov, Hoi Sing Kwok, Hirokazu Takada, and Haruyoshi Takatsu, Photoaligning hy azo-dyes physics and applications. Liquid Crystals Today 4, 1 (2005), IEEE...

S. Faetti, G. Mutinati, and I. Gerus, Measurements of the azimuthal anchoring energy at the interface between a nematic hquid crystal and photosensitive polymers. Molecular Crystals and Liquid Crystals 421, 81 (2004). 

V. P. Vorflusev, H. S. Kitzerow, and V. G. Chigrinov, Azimuthal anchoring energy in photoinduced anisotropic films. Japanese Journal of Applied Physics 34, LI 137 (1995). 

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