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Mechanism Of Electric-Field-Induced Segregation Of Additives In A Liquid-Crystal Host, Lu Lu, Vassili Sergan, Philip J. Bos Nov 2012

Mechanism Of Electric-Field-Induced Segregation Of Additives In A Liquid-Crystal Host, Lu Lu, Vassili Sergan, Philip J. Bos

Chemical Physics Publications

The mechanism for electric-field-induced segregation of additives, containing a polar group, in a host liquid crystal is proposed. It is shown that the polarity of an applied dc electric field, or the frequency of an ac electric field, strongly influences the segregation of reactive monomers containing an ester group. An explanation of this result is offered based on the association of dissolved ions with polar groups of the reactive monomers. This association is considered to cause these types of additives to drift to the cell surface in the presence of an external electric field. The described mechanism can be applied ...


Nonlocal Model For Nematic Liquid-Crystal Elastomers, R. Ennis, L. C. Malacarne, Peter Palffy-Muhoray, M. Shelley Jan 2006

Nonlocal Model For Nematic Liquid-Crystal Elastomers, R. Ennis, L. C. Malacarne, Peter Palffy-Muhoray, M. Shelley

Chemical Physics Publications

We have developed a fully nonlocal model to describe the dynamic behavior of nematic liquid-crystal elastomers. The free energy, incorporating both elastic and nematic contributions, is a function of the material displacement vector and the orientational order parameter tensor. The free energy cost of spatial variations of these order parameters is taken into account through nonlocal interactions rather than through the use of gradient expansions. We also give an expression for the Rayleigh dissipation function. The equations of motion for displacement and orientational order are obtained from the free energy and the dissipation function by the use of a Lagrangian ...


Freedericksz Transition In Polymer-Stabilized Nematic Liquid Crystals, Rui-Qing Ma, Deng-Ke Yang Feb 2000

Freedericksz Transition In Polymer-Stabilized Nematic Liquid Crystals, Rui-Qing Ma, Deng-Ke Yang

Chemical Physics Publications

We have constructed polymer-stabilized nematic liquid crystals by photopolymerizing diacrylate monomers in the nematic phase. The orientation of the liquid crystal was controlled by the polymer network. We studied the Freedericksz transition in these systems. Experimentally we studied the transition by measuring the capacitance of the liquid crystal cells as a function of applied voltage. The transition was affected profoundly by the dispersed polymer network. The threshold was higher with shorter interpolymer network distance. Theoretically we studied the systems using a two-dimensional model in which the polymer networks were represented by parallel cylinders with random location. The interaction between the ...


Nematic Order In Polymer-Stabilized Liquid Crystals, R. E. Kraig, P. L. Taylor, Ruiqing Ma, Deng-Ke Yang Oct 1998

Nematic Order In Polymer-Stabilized Liquid Crystals, R. E. Kraig, P. L. Taylor, Ruiqing Ma, Deng-Ke Yang

Chemical Physics Publications

We have studied both experimentally and theoretically how the presence of polymer fibrils can influence the ordering in liquid crystal systems. When such fibrils are formed by polymerization in a nematic solution, the polymer structure can reflect the director orientation at the time of polymerization. This anisotropic structure can be retained even when the liquid crystal is heated into its isotropic phase. We report measurements of this effect and also calculations based on a simple model of the mechanism by which the polymer fibrils can be expected to influence the nematic order of a liquid crystal matrix. A numerical solution ...