General Mesophases

by H. Pleiner
(external collaboration with P.K. Mukherjee and H.R. Brand)


First, smectic liquid crystals are investigated. They serve as model systems for micellar lamellar and ordered diblock copolymer phases and they are used for display applications. Their nonlinear behaviour as well as their electro-optic properties are of special interest [A]. Nonlinear dynamic equations (including external fields) for tilted smectic C phases are derived. Direct phase transitions from the isotropic to various smectic phases are discussed [B]. As an example, a direct isotropic to smectic A phase transition is shown (in red) that precedes the isotropic to nematic transition (in blue) for a negative crosscoupling between the nematic(S) and the smectic order parameter (ψ0) in the free energy.


Second, cholesteric liquid crystals are investigated. Although not really layered phases, their large-scale behavior is rather similar to that of smectics. Flow properties, thermo- and electromechanical couplings are prominent features on the global as well as on the local scale [C]. Generalized static as well as dynamic Lehmann-type effects are considered (cf. also Membranes, Films and Surface Waves). Symmetry and relaxing variables are discussed for the sponge (L3) phase [D]. 
Recently, the macroscopic dynamics of a homogeneous polar nematic phase has been derived [E] (for a polar nematic splay phase, cf. H. Pleiner and H.R. Brand, Europhys. Lett. 9, 243 (1989)).


Recent Publications:

preprints of the theory group


Other research topics:
Instabilities in Complex Fluids
Rheology of Complex Fluids
Liquid Crystalline Polymers and Elastomers
Membranes, Films and Surface Waves
Banana and Dolphin Phases
Unconventional Ferrofluids


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Last modified: November 8th, 2011