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Chemical Physics Publications

Banana-shaped molecules

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Full-Text Articles in Physics

Statistical Mechanics Of Bend Flexoelectricity And The Twist-Bend Phase In Bent-Core Liquid Crystals, Shaikh M. Shamid, Subas Dhakal, Jonathan V. Selinger May 2013

Statistical Mechanics Of Bend Flexoelectricity And The Twist-Bend Phase In Bent-Core Liquid Crystals, Shaikh M. Shamid, Subas Dhakal, Jonathan V. Selinger

Chemical Physics Publications

We develop a Landau theory for bend flexoelectricity in liquid crystals of bent-core molecules. In the nematic phase of the model, the bend flexoelectric coefficient increases as we reduce the temperature toward the nematic to polar phase transition. At this critical point, there is a second-order transition from high-temperature uniform nematic phase to low-temperature nonuniform polar phase composed of twist-bend or splay-bend deformations. To test the predictions of Landau theory, we perform Monte Carlo simulations to find the director and polarization configurations as functions of temperature, applied electric field, and interaction parameters.


Bundles Of Fluid Fibers Formed By Bent-Core Molecules, C. Bailey, M. Murphy, A. Eremin, Wolfgang Weissflog, Antal Jakli Mar 2010

Bundles Of Fluid Fibers Formed By Bent-Core Molecules, C. Bailey, M. Murphy, A. Eremin, Wolfgang Weissflog, Antal Jakli

Chemical Physics Publications

The internal structures, stability, and elastic properties of free-standing filament bundles of bent-core smectic liquid crystals are studied using polarizing microscopy, scanning electron microscopy, and a customized cantilever containing, temperature controlled heat stage for force measurements. We find that in bundles, the individual filaments fuse together to form semiseparable filaments with radii approximately two and three times larger than the individual fibers. We also find that the effective surface tension of wide bundles is about 10% smaller than a single filament. Finally, we describe the metastable coexistences of single fibers within the bundles that lead to bending of the bundles ...


Large Flow Birefringence Of Nematogenic Bent-Core Liquid Crystals, C. Bailey, Katalin Fodor-Csorba, Rafael Verduzco, Jim T. Gleeson, Samuel N. Sprunt, Antal Jakli Dec 2009

Large Flow Birefringence Of Nematogenic Bent-Core Liquid Crystals, C. Bailey, Katalin Fodor-Csorba, Rafael Verduzco, Jim T. Gleeson, Samuel N. Sprunt, Antal Jakli

Chemical Physics Publications

We have found that bent-core liquid crystalline materials show exceptionally large intrinsic flow birefringence in their isotropic liquid phase. This effect is more than 100 times larger than typical values measured for low molecular weight liquid crystals. The specific flow birefringence (i.e., normalized by the flow viscosity) is an order of magnitude larger than in both side-chain polymeric as well as low molecular weight liquid crystals. We propose that this large enhancement for bent-core compounds may be attributed to nanoscale smecticlike clusters that persist above the nematic-isotropic transition temperature, and shear align under shear flow; however, this mechanism has ...


Critical Behavior At The Isotropic-To-Nematic Phase Transition In A Bent-Core Liquid Crystal, D. B. Wiant, S. Stojadinovic, K. Neupane, S. Sharma, Katalin Fodor-Csorba, Antal Jakli, Jim T. Gleeson, Samuel N. Sprunt Mar 2006

Critical Behavior At The Isotropic-To-Nematic Phase Transition In A Bent-Core Liquid Crystal, D. B. Wiant, S. Stojadinovic, K. Neupane, S. Sharma, Katalin Fodor-Csorba, Antal Jakli, Jim T. Gleeson, Samuel N. Sprunt

Chemical Physics Publications

Magnetic birefringence and dynamic light scattering measurements of orientational order parameter fluctuations at the isotropic-nematic phase transition of a bent-core liquid crystal reveal a pretransitional temperature dependence consistent with the standard Landau-deGennes mean field theory. However, as follows: the transition in the bent-core compound is more weakly first order (T(NI)-T(*)approximate to 0.4 degrees C), the leading Landau coefficient is similar to 30 times lower, the viscosity associated with nematic order fluctuations is similar to 10 times higher, and the density change is similar to 10 times lower, than typically observed in calamitic (rod-shaped) liquid crystals. One ...