Frequency Behavior of the Electro-optical Effect from Colloid Particles in Polyelectrolyte Solutions with Counterion Mixtures
The electric light scattering method was used to investigate the frequency behavior of ferric oxide particles in carboxymethylcellulose solutions containing mono- and divalent counterion mixtures. The dispersion curves of suspensions, stabilized by polyelectrolyte adsorption, were analyzed in terms of three relaxations: rotational relaxation of the polymer-coated particles (at frequencies below 1 kHz), low-frequency relaxation of the bound counterions polarization (at frequencies from 1 kHz to 10 kHz) and high-frequency relaxation of the free counterions polarization (at frequencies above 60 kHz) along the particle axis. The frequency behavior of the electro-optical effect from suspensions containing polyelectrolyte with counterions mixtures was explained in accordance with the theory that the fraction of free (mono- and divalent) counterions increases with increasing the equivalent fraction of divalent ions in the mixture. Immobility of the strongly bound divalent counterions at low field strengths is supposed to reduce their contribution in the low-frequency effect in comparison to the effect from the less bound monovalent counterions.
Radeva
T
Institute of Physical Chemistry, Bulgarian Academy of Sciences, Sofia, 1113, Bulgaria