Macroscopic dynamics of polar nematic liquid crystals.
We present the macroscopic equations for polar nematic liquid crystals. We consider the case where one has both, the usual nematic director, n[over ] , characterizing quadrupolar order as well as the macroscopic polarization, P , representing polar order, but where their directions coincide and are rigidly coupled. In this case one has to choose P as the independent macroscopic variable. Such equations are expected to be relevant in connection with nematic phases with unusual properties found recently in compounds composed of banana-shaped molecules. Among the effects predicted, which are absent in conventional nematic liquid crystals showing only quadrupolar order, are pyro-electricity and its analogs for density and for concentration in mixtures as well as a flow alignment behavior, which is more complex than in usual low molecular weight nematics. We also discuss the formation of defect structures expected in such systems.
Brand
Helmut R
HR
Theoretische Physik III, Universität Bayreuth, 95440 Bayreuth, Germany and Max Planck Institute for Polymer Research, 55021 Mainz, Germany. brand@uni-bayreuth.de
Pleiner
Harald
H
Ziebert
Falko
F