Evaluation of the viscoelastic properties of a nematic dimer by cone-and-plate rheo-nuclear magnetic resonance spectroscopy and comparison with Leslie-Ericksen theory

The viscoelastic behavior of a nematic dimer is studied by deuteron (2H) nuclear magnetic resonance (NMR) spectroscopy using a cone-and-plate rheometer. From the 2H NMR spectra, monitored as a function of the shear rate, the orientation of the director relative to the magnetic field is obtained. Analysis of this experiment, using an analytical and a numerical solution of the Leslie–Ericksen equations, gives detailed information on the viscoelastic properties of the dimer. In particular, the two Leslie viscosities α2 and α3 and the three-dimensional director distribution are determined. The analysis reveals that α2 and α3 are both positive, that is, the dimer is of the flow-aligning type, and the director is tilted by an angle of about 33° from the magnetic field toward the velocity axis.