Comparison of the Dielectric Relaxation Data for the Isotropic and Nematic Phases of Three Homologous Series: nCb, nOCB and nPCH, (n =5÷8)

Abstract

Results of dielectric studies of three homologous series: n-alkyl-cyanobiphenyls - nCB, n-alkyloxy-cyanobiphenyls - nOCB, and trans-4-(4′-n-alkyl-cyclohexyl)-cyanobenzene - nPCH, with n from 5 to 8, are presented. The parameters characterizing the rotational motions of the molecules around their short axes in the nematic and isotropic phases were derived (dielectric increments, relaxation times, activation enthalpies, retardation factors, nematic potentials, order parameters). Comparative analyses of the parameters in respect to the lengths of the terminal groups and the structures of the molecular cores are given.

Key Words:

• dielectric properties
• nematics
• nCBs
• nOCBs
• nPCHs