Saddle-splay Elasticity Research Articles

Magnetic field effect on periodic stripe domains in nematic liquid crystals.

Hybrid aligned nematic films placed onto an isotropic fluid substrate exhibit an unusual periodic stripe domain structure that appears only when the thickness of the film is smaller than a few tenths of a micrometer. We investigated the effect of a magnetic field on the threshold between the periodic stripe domains and the aperiodic deformed structure of the director. As experimentally observed, a magnetic field applied along the stripe domains favors a nonperiodic state with the director undistorted in the horizontal plane. The experimental findings are confirmed by a theory that takes into account not only the usual type of the elastic distortions, but also the so-called saddle-splay elasticity. A comparison of the experimental and theoretical data allows one to estimate that the saddle-splay elastic constant ${\mathit{K}}_{24}$ is of the same order of magnitude as the bulk elastic constants; this result agrees with independent studies of confined liquid crystal systems.

Saddle-splay elasticity of nematic structures confined to a cylindrical capillary.

The stability of nematic structures within a cylindrical capillary whose wall exhibits a homeotropic boundary condition is studied. The structures are obtained numerically from Euler-Lagrange equations resulting from the minimization of the Frank free energy functional. Stability diagrams are presented showing dependence on elastic properties, surface anchoring, and external transversal field strength. Emphasis is given to the effects of the saddle-splay elastic constant (${\mathit{K}}_{24}$), which plays an important role in the weak anchoring regime. A new structure---the planar polar structure with two line defects---is predicted. It is shown that it is stable in a finite interval of the external field strength in the strong anchoring regime.

Molecular asymmetry and saddle-splay elasticity in lipid bilayers

Molecular asymmetry and saddle-splay elasticity in lipid bilayers