133 research outputs found
Poisson-bracket approach to the dynamics of bent-core molecules
We generalize our previous work on the phase stability and hydrodynamic of
polar liquid crystals possessing local uniaxial -symmetry to
biaxial systems exhibiting local -symmetry. Our work is motivated by
the recently discovered examples of thermotropic biaxial nematic liquid
crystals comprising bent-core mesogens, whose molecular structure is
characterized by a non-polar body axis as well as a polar axis
along the bisector of the bent mesogenic core which is coincident
with a large, transverse dipole moment. The free energy for this system differs
from that of biaxial nematic liquid crystals in that it contains terms
violating the symmetry. We show that, in spite of a
general splay instability associated with these parity-odd terms, a uniform
polarized biaxial state can be stable in a range of parameters. We then derive
the hydrodynamic equations of the system, via the Poisson-bracket formalism, in
the polarized state and comment on the structure of the corresponding linear
hydrodynamic modes. In our Poisson-bracket derivation, we also compute the
flow-alignment parameters along the three symmetry axes in terms of microscopic
parameters associated with the molecular geometry of the constituent biaxial
mesogens.Comment: 16 pages, RevTeX, 1 figur
The solution of the puzzle of smectic-Q: The phase structure and the origin of spontaneous chirality
The so-called smectic-Q (SmQ) liquid crystal phase was discovered in 1983 in rod-like molecules, but its structure remain unclear in spite of numerous attempts to solve it. Herein, we report what we believe to be the solution: A unique bicontinuous phase that is non-cubic and is made up of orthogonal twisted columns with planar 4-way junctions. While SmQ had only been observed in chiral compounds, we show that this chiral phase forms also in achiral materials through spontaneous symmetry breaking. The results strongly support the idea of a helical substructure of bicontinuous phases and long-range homochirality being sustained by helicity-matching at network junctions. The model also explains the triangular shape of double-gyroid domains growing within a SmQ environment. SmQ-forming materials hold potential for applications such as circularly polarized light emitters that require no alignment or asymmetric synthesis
ChemInform Abstract: Inversion of the Cyclotribenzylene Cone in a Columnar Mesophase: A Potential Way to Ferroelectric Materials.
On the Molecular Requirements for the Stabilisation of Thermotropic Biaxial Ordering in Rod-Plate Nematics
New Series of Biforked Mesogens Derived from 3,4-Dialkoxycinnamic Acid and 3-(3′4′-Dialkoxyphenyl)Propanoic Acid
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