The azimuthal anchoring energy at the interface between the nematic liquid crystal pentylcyanobiphenyl (5CB) and an obliquely evaporated SiOx substrate is measured by using a reflectometric method. The time response of the director at the surface is investigated and two very different regimes are evidenced. The azimuthal anchoring energy coefficient exhibits an almost-critical behaviour near the clearing temperature and is almost independent on the thickness d of the SiOx layer but it exhibits a sharp decrease for d ≤ dc ≈ 25 Å. The anchoring function is found to depend on the azimuthal director angle φ as W(φ) = Wa/2 sin2(φ). © 1992, Taylor & Francis Group, LLC. All rights reserved.

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