DIELECTRIC INVESTIGATION OF ISOTROPIC AND ANISOTROPIC SOLUTIONS OF CELLULOSE-ACETATE IN DIOXANE

The dielectric and optical characteristics of a sample of cellulose ac etate (DS = 2.45) in dioxane solutions were studied at 10-50 degrees C over the range of concentration 10-50 wt% to include both isotropic a nd anisotropic phases. The study showed that the loss maximum, epsilon (max)'', magnitude of polarization, (epsilon(0) - epsilon(infinity)), static dielectric constant, epsilon(0), time of relatation, (2 pi f(m) )(-1), and refractive index, n(D), steadily increase with concentratio n up to the critical concentration (41 wt%) and then decrease. The mea n-square dipole moment, [g mu(2)], decreases steadily up to the critic al concentration then remains nearly constant, indicating that the iso tropic solution changes to anisotropic, with smaller mean-square dipol e moment. Comparison between the results of cellulose acetate (CA) and those of hydroxypropyl cellulose (HPC) reveals that, at the critical concentration in dioxane, the cholesteric structure of HPC possesses a greater mean-square dipole moment with higher temperature coefficient than does CA. The activation energy of the relaxation process for hyd roxypropyl cellulose is higher, indicating a greater intrachain intera ction compared with cellulose acetate.