In this report we present the results of experimental investigations of decay Poiseuille flow of 5 CB through the porous polymer (PET) film of thickness 23 μm with submicron diameters d of pores. Previously, the method of the decay Poiseuille flow was successfully used, elaborated for the shear viscosity measurements of NLC stabilized by surfaces in flat capillaries [1]. The samples of porous polymer films can be considered as a number N of cylindrical capillaries, connected by parallel schema with the effective hydrodynamic resistanceN, expressed as ZN = Z/N. It makes possible to use the simple exponential law ΔH(t) = ΔH(0) exp(-t/τ) for the time dependence of the difference of levels DH of a liquid in the open tubes of diameter D separated by the central part of LC cell, which includes the porous film. The decay time τ is proportional to the effective coefficient of the shear viscosity ηeff. The experimental ΔH(t) follows the simple theoretical expression mentioned above. It corresponds to the Newtonian character of the flow and makes possible to determine the ηeff for different d and temperatures.
The analysis of experimental data was made taking into account the influence of weak surface anchoring effects on the orientational structure of liquid crystals. The obtained results can be used for description of electrooptical response of porous films, filled with LC [2].
Acknowledgements: This work was supported by the RFBR [project no. 16-33-00802 mol_а.].
1. Pasechnik S. V., Chigrinov V. G., Shmeliova D. V., Tsvetkov V. A., Voronov A. N. Anisotropic shear viscosity in nematic liquid crystals: new optical measurement method, Liquid Cryst., 31, 585 (2004).
2. D. Semerenko, D. Shmeliova, S. Pasechnik, A. Murauskii, V. Tsvetkov, V. Chigrinov. Optically controlled transmission of porous polyethylene terephthalate films filled with nematic liquid crystal. Optics Letters, 2010 35(13), 2155-2157 (2010).
