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Soft Matter and Biological Physics

Eur. Phys. J. E 7, 267-272 (2002)
DOI: 10.1140/epje/i200101176

Rotational viscosity enhancement in nematic liquid crystal near a charged surface

A.V. Zakharov and R.Y. Dong

Department of Physics and Astronomy, Brandon University, Brandon, Manitoba R7A 6A9, Canada


(Received 22 November 2001 and Received in final form 31 January 2002)

The effective rotational viscosity coefficient $\gamma^{\rm
eff}_1$ and flow alignment angle $\theta_{\rm eff}$ are investigated for polar liquid crystals (LCs), such as 4- n-octyloxy- $4^{\prime}$-cyanobiphenyl (8OCB), in the vicinity of a charged bounding surface. $\theta_{\rm eff}$ is calculated using the Ericksen-Leslie theory, both for stationary and nonstationary regimes. Calculations of $\gamma^{\rm
eff}_1$, both for homeotropic and planar alignment of 8OCB molecules, at a charged indium tin oxide(ITO)-coated glass plate show an additional contribution to $\gamma^{\rm
eff}_1$ up to $7.8 \%$. The nonequilibrium flow alignment angle $\theta_{\rm eff} (\tau)$ is also calculated for the surface region bounded by $0.1 \le y \le 3.0$  $\mu $m. Transition from a tumbling situation to a flow aligning regime can occur near the charged boundary surface.

61.30.Cz - Molecular and microscopic models and theories of liquid crystal structure.
66.20.+d - Viscosity of liquids; diffusive momentum transport.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2002