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Chemical Physics Publications

Mixtures

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Full-Text Articles in Physics

Photoisomerization-Controlled Phase Segregation In A Submicron Confined Azonematic Liquid Crystal, B. Zupančič, S. Diez-Berart, D. Finotello, Oleg Lavrentovich, V. Zalar Jun 2012

Photoisomerization-Controlled Phase Segregation In A Submicron Confined Azonematic Liquid Crystal, B. Zupančič, S. Diez-Berart, D. Finotello, Oleg Lavrentovich, V. Zalar

Chemical Physics Publications

Deuteron nuclear magnetic resonance is used to study the phase segregation behavior of photoisomerizable liquid crystal diheptylazobenzene (7AB) confined into cylindrical pores of Anopore membranes. It is demonstrated that the concentration of both components in a binary trans-7AB and cis-7AB mixture can be controlled dynamically using UV-illumination stimulated trans-to-cisphotoisomerization and thermally induced cis-to-trans backisomerization. The so far elusive temperature-concentration phase diagram of such system is determined by comparative analysis of the behavior in bulk, thin-planar, and Anopore-confining geometry.


Maier-Saupe-Type Theory Of Ferroelectric Nanoparticles In Nematic Liquid Crystals, Lena M. Lopatina, Jonathan V. Selinger Oct 2011

Maier-Saupe-Type Theory Of Ferroelectric Nanoparticles In Nematic Liquid Crystals, Lena M. Lopatina, Jonathan V. Selinger

Chemical Physics Publications

Several experiments have reported that ferroelectric nanoparticles have drastic effects on nematic liquid crystals-increasing the isotropic-nematic transition temperature by about 5 K, and greatly increasing the sensitivity to applied electric fields. In a recent paper [Lopatina and Selinger, Phys. Rev. Lett. 102, 197802 (2009)], we modeled these effects through a Landau theory, based on coupled orientational order parameters for the liquid crystal and the nanoparticles. This model has one important limitation: Like all Landau theories, it involves an expansion of the free energy in powers of the order parameters, and hence it overestimates the order parameters that occur in the ...


Effect Of Trans-Cis Photoisomerization On Phase Equilibria And Phase Transition Of Liquid-Crystalline Azobenzene Chromophore And Its Blends With Reactive Mesogenic Diacrylate, Namil Kim, Quan Li, Thein Kyu Mar 2011

Effect Of Trans-Cis Photoisomerization On Phase Equilibria And Phase Transition Of Liquid-Crystalline Azobenzene Chromophore And Its Blends With Reactive Mesogenic Diacrylate, Namil Kim, Quan Li, Thein Kyu

Chemical Physics Publications

Photoisomerization-induced phase transition of neat liquid-crystalline azobenzene chromophore (LCAC) and its effect on phase diagrams of its mixtures with reactive mesogenic diacrylate monomer (RM257) have been investigated experimentally and theoretically. Upon irradiation with ultraviolet light, the nematic phase of LCAC transformed to isotropic, while the crystal phase showed corrugated textures on the surface (i.e., ripples). The phase-transition temperatures and corresponding morphologies of the blends have been investigated by means of differential scanning calorimetry and optical microscopy. A theoretical phase diagram of a binary nematic and crystalline system was constructed by self-consistently solving the combined free energies of Flory-Huggins, Maier-Saupe ...


Distance Of Closest Approach Of Two Arbitrary Hard Ellipses In Two Dimensions, Xiaoyu Zheng, Peter Palffy-Muhoray Jun 2007

Distance Of Closest Approach Of Two Arbitrary Hard Ellipses In Two Dimensions, Xiaoyu Zheng, Peter Palffy-Muhoray

Chemical Physics Publications

The distance of closest approach of hard particles is a key parameter of their interaction and plays an important role in the resulting phase behavior. For nonspherical particles, the distance of closest approach depends on orientation, and its calculation is surprisingly difficult. Although overlap criteria have been developed for use in computer simulations [ Vieillard-Baron J. Chem. Phys. 56 4729 (1972); Perram and Wertheim J. Comput. Phys. 58 409 (1985)], no analytic solutions have been obtained for the distance of closest approach of ellipsoids in three dimensions, or, until now, for ellipses in two dimensions. We have derived an analytic expression ...


Distance Of Closest Approach Of Two Arbitrary Hard Ellipsoids, Xiaoyu Zheng, Wilder Iglesias, Peter Palffy-Muhoray Jun 2007

Distance Of Closest Approach Of Two Arbitrary Hard Ellipsoids, Xiaoyu Zheng, Wilder Iglesias, Peter Palffy-Muhoray

Chemical Physics Publications

The distance of closest approach of hard particles is a key parameter of their interaction and plays an important role in the resulting phase behavior. For nonspherical particles, the distance of closest approach depends on orientation, and its calculation is surprisingly difficult. Although overlap criteria have been developed for use in computer simulations [ Vieillard-Baron J. Chem. Phys. 56 4729 (1972); Perram and Wertheim J. Comput. Phys. 58 409 (1985)], no analytic solutions have been obtained for the distance of closest approach of ellipsoids in three dimensions, or, until now, for ellipses in two dimensions. We have derived an analytic expression ...


Effect Of Director Distortions On Morphologies Of Phase Separation In Liquid Crystals, D. Voloschenko, Oleg P. Pishnyak, Sergij V. Shiyanovskii, Oleg Lavrentovich Jun 2002

Effect Of Director Distortions On Morphologies Of Phase Separation In Liquid Crystals, D. Voloschenko, Oleg P. Pishnyak, Sergij V. Shiyanovskii, Oleg Lavrentovich

Chemical Physics Publications

We study phase separation from a nematic liquid crystal with spatially nonuniform director gradients. Particles of a phase-separated component, which is either an isotropic fluid (silicone oil) or a nonmesogenic photopolymer, accumulate in the regions with the strongest director distortions, thus reducing the overall energy of the system.