Viscosity coefficients of nematic liquid crystals: I. Oscillating plate viscometer measurements and rotational viscosity measurements: K15

Improvements in the oscillating plate and rotational viscosity measurements are described and data presented for 4-n-pentyl-4-cyanobiphenyl (K15). The influence of the magnitude of the magnetic field on the viscosity coefficients is explored and the limiting field which has to be achieved for field-independent values is identified. The field dependence of the viscosity coefficients is compared with theoretical prediction. Comparison of this data with earlier measurements indicates the limitations of the use of lower field strengths. Combining the data from the measured viscosities, the Leslie–Ericksen coefficients are calculated.