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

The dielectric and optical characteristics of a sample of cellulose acetate (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 and 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 concentration up to the critical concentration (41 wt%) and then decrease. The mean-square dipole moment, [g mu(2)], decreases steadily up to the critical concentration then remains nearly constant, indicating that the isotropic solution changes to anisotropic, with smaller mean-square dipole 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 hydroxypropyl cellulose is higher, indicating a greater intrachain interaction compared with cellulose acetate.