Dielectric dispersion study of coexisting phases of aqueous polymeric solution: Poly(vinyl alcohol) plus poly(vinyl pyrrolidone) two-phase systems

The complex dielectric constant epsilon*(omega) = epsilon' - j epsilon '', electric modulus M*(omega) = M' + jM '', impedance Z*(omega) - Z' - jZ '' and ac conductivity dispersion behaviour of 5, 10 and 15 wt% concentration aqueous solutions of poly(vinyl alcohol) (PVA) (14 000 and 77 000 g mol(-1)) and poly(vinyl pyrrolidone) (PVP) (24000, 40000 and 360000 gmol(-1)) and their binary mixtures were investigated in the frequency range 20 Hz to 1 MHz at 25 degrees C. Analysis of dielectric constant values confirms that hydrophilic effect of PVA in aqueous solution increases the real part of dielectric constant epsilon', whereas for aqueous PVP solutions the hydrophobic effect masks the hydrophilic effect, which reduces epsilon' values below 10 kHz. Low-frequency dielectric constant of these aqueous polymeric systems is sensitive to ionic conduction and electrode polarization. The monotonous change in various electrical properties with change in volume percentage of mixture constituents indicates that individual aqueous polymer system retains their own electrical properties in the aqueous two-phase polymeric system. (c) 2007 Elsevier Ltd. All rights reserved.