Biomedical subjects

Mikhail A Osipov

Publications and source records attributed to Mikhail A Osipov.

3 recordsLinked to original sources

PubMed2005

Induced and spontaneous deracemization in bent-core liquid crystal phases and in other phases doped with bent-core molecules.

Recently discovered chiral properties of several bent-core smectic liquid crystal phases are summarized and discussed in detail under the assumption that typical bent-core molecules may exist in chiral conformational states and are achiral only on average. Results of atomistic computer simulations are presented which indicate the existence of strongly chiral conformational states for typical bent-core mesogens. A theory is developed which describes a possible shift of equilibrium between left- and right-handed conformations in a macroscopically chiral phase. The theory describes a chirality induction in the B2 bent-core phase and a reduction of the helical pitch in cholesteric and chiral SmC* phases doped with bent-core molecules. Finally, the possibility of spontaneous deracemization in bent-core smectic phases is discussed in detail.

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PubMed2004

Reflection of light at structured chiral interfaces.

Modified boundary conditions and general surface constitutive equations are derived for a very thin interface with some internal structure that separates two different media. The modified boundary conditions are reduced to the standard ones for an idealized steplike sharp interface without additional structure. These modified boundary conditions together with surface constitutive equations and Maxwell equations in the bulk form a complete set of macroscopic equations to describe optical properties of planar interfaces with thicknesses much less then the wavelength of light. In particular, two-dimensional chiral surfaces are considered that are characterized by surface gyrotropic coefficients even if the two different bulk media and the interface are made of nonchiral materials. It is shown that the rotation of the polarization state should occur for the light reflected from such a surface. This result is supported by recent experimental data.

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PubMed2003

Orientational ordering and chiral symmetry breaking in organic monolayers composed of disklike mesogenic molecules: molecular theory and computer simulations.

Orientational ordering of disklike molecules on a flat surface is investigated using a molecular-statistical theory and Monte-Carlo simulations. The theory is based on the two-dimensional orientational order parameter for molecules with a threefold symmetry axis, and on a simple model interaction potential which has been derived taking into consideration only the symmetry of basic molecular structure. The theory reveals three different anisotropic phases. One of them exactly corresponds to the structure which has recently been observed experimentally in self-assembling monolayers of discotic mesogenic molecules on a pyrolitic graphite surface. This is a two-dimensional (2D) chiral anisotropic phase composed of nonchiral molecules. The phase consists of three sublattices with different orientational order. One sublattice is orientationally disordered, while the other two sublattices are ordered with the same scalar order parameter and different orientations of the ordering tensor. Both order parameters of the directions of ordering are determined self-consistently by minimizing the total free energy of the system. The detailed structure of this unusual phase is also confirmed by the results of Monte Carlo simulations based on the same model interaction potential. The results of the theory qualitatively explain existing experimental data and also shed some light on the origin of supramolecular structures observed in 3D columnar phases composed of similar molecules.

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