Zz. Zhong et al., DIELECTRIC RELAXATIONS OF A SMECTIC SIDE-CHAIN LIQUID-CRYSTALLINE POLYMER IN DIFFERENT ALIGNMENT STATES, Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals, 238, 1994, pp. 129-145
The complex dielectric constant has been measured for a polyvinyl-ethe
r based cyano-biphenyl side-chain liquid-crystalline polymer over the
temperature range of 100-400 K and frequency range of 10-10(5) Hz. In
the smectic-A phase, both homogeneous and homeotropic alignments were
achieved with a 7-Tesla magnetic field by slowly cooling the samples d
own from the isotropic phase to room temperature. The low-frequency de
lta loss peaks are suppressed in the homogeneous state and enhanced in
the homeotropic state while high-frequency alpha loss peaks are enhan
ced in the homogeneous and almost absent in the homeotropic. The Arrhe
nius plot of each process shows a rapid decrease in the relaxation fre
quency as the temperature approaches T(g), which may somehow reflect t
he glassy behavior of the polymer backbone and has been analyzed by WL
F and Vogel-Fulcher equations. The results from two samples with diffe
rent degree of polymerization are compared in terms of T(g).