| The signs of the Leslie viscosities alpha_2 and alpha_3 for rod-like and disc-like molecules in the uniaxial nematic phase are calculated using a dynamic molecular mean field theory based upon a Fokker-Planck equation. The viscosities are shown to depend on the particle geometry and alignment order parameters. In particular, for positive degree of alignment S_2, the calculations tend to confirm Carlsson's conjecture relating the signs of the two viscosities to the particle geometry. Furthermore, a transition in the signs of alpha_2 for discotics and alpha_3 for nematics is predicted with increasing order parameter S_2 in accord with recent experiments. For small degree of alignment S_2, the results reproduce previous calculations obtained by Hess in a truncation approximation. The qualitative flow behavior (e.g., tumbling) depends upon the signs of these viscosities.
for LaTeX users @article{MKroger1997-293,
author = {M. Kr\"oger and H. S. Sellers},
title = {On the signs of the Leslie viscosities alpha_2 and alpha_3 for nematics and discotic nematics},
journal = {Mol. Cryst. Liq. Cryst.},
volume = {293},
pages = {17-28},
year = {1997}
}
\bibitem{MKroger1997-293} M. Kr\"oger, H.S. Sellers,
On the signs of the Leslie viscosities alpha_2 and alpha_3 for nematics and discotic nematics,
Mol. Cryst. Liq. Cryst. {\bf 293} (1997) 17-28.MKroger1997-293
M. Kr\"oger, H.S. Sellers
On the signs of the Leslie viscosities alpha_2 and alpha_3 for nematics and discotic nematics
Mol. Cryst. Liq. Cryst.,293,1997,17-28 |
mk@mat.ethz.ch
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