Investigation of hydration of macromolecules. II. Studies on poly-(vinyl-alcohol) solutions by microwave dielectric method.

Microwave conductivity and dielectric condstant of poly-(vinyl-alcohol) (PVA) solutions of 0--10 per cent were determined at 2--4 GHz frequency in the temperature range from 25 degrees C to 35 degrees C. The low-frequency conductivities of the solutions were measured at 20 kHz in the same concentration and temperature range. Microwave conductivity was proportional to the square of frequency, and the axial section extrapolated to zero frequency was higher than low-frequency conductivity. This difference in conductivity can probably be attributed to the relaxation processes of water molecules interacting directly with macromolecules. The relaxation wavelength calculated from the frequency dependence of microwave conductivity increased and the dielectric constant of the solutions decreased with increasing macromolecular concentration in a linear way. The activation energy calculated from its temperature dependence was 4.0 +/- 1.0 kcal/mol. The products of self-diffusion coefficient and macroviscosity were compared with that of self-diffusion coefficient and microviscosity calculated from relaxation wavelength. From this the conclusion can be drawn that the self-diffusion of water is influenced by the concentration dependent microviscosity. The hydration numbers calculated by different methods give divergen results the discussion of which requires further investigations.