title: Optical measurement of azimuthal anchoring strength in nematic liquid crystals.
abstract: We have observed the azimuthal switching at the interface of nematic liquid crystals (LCs) and the aligning substrate, induced by the planar electric field of a fine comb electrode. Optical transmittance as a function of applied voltage was modeled by both the elastic theory with rigid anchoring and the Landau-de Gennes theory with the interfacial energy expression 1/2Wtr[(Q two down arrows -Q two down arrows (0))(2)], where Q two down arrows is the liquid crystal order parameter and Q two down arrows (0) is the surface order parameter induced by the aligning substrate. Optical data on the in-plane switching LC cells were found to differ qualitatively with the predictions of the rigid anchoring model but to agree well with those of the Landau-de Gennes theory. We obtain not only the strength W of the azimuthal anchoring, but also find the surface order parameter S(surface) to be 20-30 % less than that of the bulk. The optically measured azimuthal anchoring strength is in good agreement with the literature values determined through other means.
authors.affiliation: Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, China.
authors.forename: Baoshe
authors.initials: B
authors.lastname: Zhang
authors.forename: Ping
authors.initials: P
authors.lastname: Sheng
authors.forename: Hoi S
authors.initials: HS
authors.lastname: Kwok