TEMPERATURE-DEPENDENCE OF STATIC DIELECTRIC PERMITTIVITY AND DIPOLE-MOMENTS OF POLY(N-VINYLCARBAZOLE)

The dipole moment has been measured for various stereostructural forms of poly(N-vinylcarbazole) (PVK) in solution in 1,4-dioxane and in tol uene in the temperature range 288-338 K. The dielectric and dipole mom ent data were correlated with the stereostructure of PVK. The dipole m oment behaviour of various types of PVK, prepared using different cata lyst systems, may be explained in terms of 3/1, 2/1 or all-trans seque nces of syndiotactic PVK. All PVK samples showed a positive temperatur e coefficient of dipole moment but to a different extent. PVK with low est isotacticity (prepared with a free-radical catalyst) had the large st temperature coefficient, suggesting that this structure was more se nsitive to changes in temperature. However, the dielectric data for ca tionically prepared PVK appear to indicate a more random coil-type of configuration or possibly a segmental, rod-like structure in which the dipole moment vectors of groups of carbazole groups are randomly orie nted but remain approximately perpendicular to the long axis of the mo lecule, resulting in only a small temperature coefficient of dipole mo ment.