Effective frequency-dependent anchoring coefficient and rotational viscosity of nematic liquid crystals

The effective rotational viscosity and polar anchoring coefficient of a nematic liquid crystal were determined using electro-optical response by changing the frequency of the electric field in the kilohertz range. Both quantities monotonically decreased with an increase in the frequency and converged to a certain value at several tens of kilohertz. The effective rotational viscosity changes more than the order of magnitude in experimental range. On the other hand, the effective value of anchoring coefficient changes several times. We tried to explain the trends with the effect of an electric field induced by the motion of ionic impurity in liquid crystal.

► Liquid crystal viscosity and anchoring are measured for varying electric frequency.
► Viscosity and anchoring monotonically decrease with an increase in frequency.
► Viscosity and anchoring converge to a certain value at several tens of kilohertz.
► We explain the trends with electric field induced by the motion of ionic impurity.