Role of surface interactions in the dynamics of chiral isopentylcyanobiphenyl mixed with Al2O3 powder as studied by dielectric spectroscopy: numerical analysis.

The results of dielectric measurements for a mixture of chiral liquid crystal 5CB with Al(2)O(3) powder are given. A detailed analysis of the dielectric spectra enabled us to obtain information about the influence of the Al(2)O(3) grains on the dynamics of the liquid-crystal molecules. Numerical analysis of the results confirmed that the dielectric spectra obtained are complex. In the low-frequency range they are dominated by ionic conductivity while in the whole frequency range two maxima appear. One of them is related to rotations of the molecules around their short axes. In the isotropic phase the corresponding values of the relaxation times are very close to those for bulk 5CB. Relaxation and conduction processes can be described by a Vogel-Fulcher-Tammann function. In the cholesteric phase, rotation of 5CB molecules trapped in the pores of Al(2)O(3) occurs. Another relaxation process results from dynamics of 5CB molecules anchoring to Al(2)O(3) grains. The temperature dependence of relaxation times related to this process is nonmonotonic.