Anchoring coefficient

Surface Anchoring Coefficients Measured by Dynamic Light Scattering... 

Fig. 4.9. Scattering geometry for measurements of (a) azimuthal and (b) zenithal anchoring coefficient, n is the director, i and / the polarisations of the incoming and outgoing beams, and fei and fcf the corresponding wave vectors.

A comment should be added on the rotational viscosity of the sample in the experiment. It can easily be shown that in the case of azimuthal anchoring measurements, the viscosity entering the analysis equals the rotational viscosity 71. When measuring the zenithal anchoring coefficient, the effective viscosity has to be corrected according to the scattering geometry. However, in first approximation the pure splay mode viscosity is sufficient. 

Table 4.2. Comparison of anchoring energy coefficients of 4-n-pentyI-4 -cyanobiphenyl (5CB) at T = 32° C and 4-n-octyl-4-cyanobiphenyl (8CB) at T = 37° C on rubbed Nylon and photosensitive poly-(vinyl)-cinnamate. Different anchoring coefficients on rubbed Nylon are achieved by different rubbing strengths.

Fig. 4.10. Relaxation time t of the twist fluctuation mode circles) as a function of sample thickness d. For thicknesses below 3 (im a parabolic behaviour is observed solid line) and in this range the anchoring coefficient can be determined. For larger thicknesses the influence of higher fluctuation modes becomes apparent and the relaxation time decreases and approaches its bulk value [32].

Fig. 4.11. (a) Aging, as observed through the time dependence of the azimuthal anchoring coefficient for 5CB on UV aligned poly-(vinyl-cinnamate) (b) Aging, as observed through the offset parameter h [59]. 

Fig. 4.12. (a) Temperature dependence of azimuthal Wtp dots) and zenithal Wo (squares) anchoring coefficients for nematic 5CB on rubbed Nylon with Tni being the transition temperature into the isotropic phase (b) A comparison of the ratios of the two anchoring coefficients W jW p (circles) with the ratio of the corresponding Frank elastic constants KijK2 [Q5](solid line) [64]. 

D. Subacius, V. M. Pergamenshchik, and O. D. Lavrentovicha, Measurement of polar anchoring coefficient for nematic cell with high pretilt angle, Appl. Phys. Lett. 67 (2), 214 (1995)... 

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