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Full-Text Articles in Physics
Orientation And Surface Anchoring Of Nematic Liquid Crystals On Linearly Polymerized Photopolymers, H. G. Galabova, David W. Allender, J. Chen
Orientation And Surface Anchoring Of Nematic Liquid Crystals On Linearly Polymerized Photopolymers, H. G. Galabova, David W. Allender, J. Chen
David W Allender
The liquid crystal orientation on a poly(vinyl cinnamate) or poly(vinyl 4-methoxy-cinnamate) coated solid substrate exposed to linearly polarized UV light has been studied. The angular distribution of the polymer side chains and the photoreaction products was derived as a function of exposure time using a simple assumption about the probability for crosslinking of two side chains. The liquid crystal was assumed to be weakly anchored to the surface but have a degree of order and orientation determined from those of the polymer side chains. The polar and the azimuthal surface coefficients were estimated as a function of exposure time using …
Surface-Layer Phase-Transitions In Nematic Liquid-Crystals, Natasha Kothekar, David W. Allender, R. M. Hornreich
Surface-Layer Phase-Transitions In Nematic Liquid-Crystals, Natasha Kothekar, David W. Allender, R. M. Hornreich
David W Allender
Surface-layer transitions in nematogenic materials characterized by a preferential planar surface interaction linear in the order parameter have been studied theoretically at temperatures above the bulk transition (T(NI)). The coupled Euler-Lagrange nonlinear differential equations obtained from the Landau-de Gennes free energy were solved exactly by numerical integration. This problem had been studied previously employing various limits and approximations with several differences in the phase diagram reported. The exact results allow one to determine which of these differences are artifacts of the approximations used and which are dependent upon the ratio of elastic constants. It is found, for physically relevant elastic …
Theory Of A Symmetry-Breaking Phase-Transition In A Surface-Layer Of Nematic Liquid-Crystal, Y. L'Vov, R. M. Hornreich, David W. Allender
Theory Of A Symmetry-Breaking Phase-Transition In A Surface-Layer Of Nematic Liquid-Crystal, Y. L'Vov, R. M. Hornreich, David W. Allender
David W Allender
For a surface interaction linear in the order parameter and favoring an orientation in which liquid-crystalline molecules lie parallel to the surface (but which is independent of whether the orientation is uniaxial or isotropic in the bounding plane), a symmetry-breaking phase transition in a surface layer is possible at temperatures above that of the bulk isotropic to nematic transition. At the surface transition, the high-temperature in-plane isotropic state becomes unstable with respect to a biaxial phase, the transition being continuous and therefore of-the Berezinskii-Kosterlitz-Thouless (BKT) type, It is expected to occur for intermediate surface couplings but not at very weak …
Calorimetric Study Of Nematic Prewetting, Xuewu Liu, David W. Allender, D. Finotello
Calorimetric Study Of Nematic Prewetting, Xuewu Liu, David W. Allender, D. Finotello
David W Allender
We report specific-heat measurements for a series of liquid crystals imbedded in a porous cylindrical geometry. Above the nematic-to-isotropic transition and dependent on nematic width (or chain length), the specific heat shows a small peak. In analogy to known ellipsometry results, the peak is believed to be the signature of a nematic prewetting transition.