Dielectric relaxation analysis was carried out on the main chain thermotropic liquid
crystalline copolyesteramide Vectra B950. The dielectric spectra of Vectra B950 show four relaxations,
instead of three as cited in the literature. These correspond, from high to low temperature, to the glass
transition, the rotation of hydroxynaphthoic acid moieties, the rotation of terephthalic acid moieties, and
the combined rotation of terephthalic acid and aminophenol moieties. The combination of TSD and DMA
analysis made it possible to distinguish between dipole and charge relaxations. Although the TSD and
the dielectric results compare well for the low-temperature dipole relaxations, they are not directly
comparable for the α relaxation. TSD experiments reveal that free charges have a significant influence
on the α relaxation.
Wrinkling of elastomeric coatings by an electric field is reported. The associated changes in the coating's optical properties yield switchable mirrors and windows. The field Ec needed to induce wrinkling is a factor of 4.4 lower than the theoretically predicted value, which is attributed to space-charge injection.
In this paper we discuss the use of dielectric
spectroscopy as a means to study the morphology
of polymer blends. We have investigated a model system of
thermotropic liquid crystalline polymer (Vectra
B950) fibers lined up in a polypropylene (Stamylan P 13E10) matrix.
The appearance of interfacial
polarization at the interface between the two polymeric phases makes it
possible to calculate the shape
of the inclusions. For this purpose a formula is derived, which
gives the shape factor of a distorted fiber
as a function of the distortion amplitude. The calculated shapes
of the fibers agree very well with the
actual shapes, despite the approximations made. The agreement was
proven by performing dielectric
measurements under an optical microscope. As expected, the growth
rate of thick fibers is smaller than
that of thinner ones. A comparison between experiments under the
microscope and in a dielectric sample
holder showed the importance of the heating rate on the breakup of the
fibers.
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