FREQUENCY BEHAVIOR OF THE ELECTROOPTICAL EFFECT FROM COLLOID PARTICLES IN POLYELECTROLYTE SOLUTIONS WITH COUNTERION MIXTURES

The electric light scattering method was used to investigate the frequ ency behavior of ferric oxide particles in carboxymethylcellulose solu tions containing mono- and divalent counterion mixtures. The dispersio n curves of suspensions, stabilized by polyelectrolyte adsorption, wer e 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. T he frequency behavior of the electro-optical effect from suspensions c ontaining polyelectrolyte with counterions mixtures was explained in a ccordance with the theory that the fraction of free (mono- and divalen t) counterions increases with increasing the equivalent fraction of di valent ions in the mixture. Immobility of the strongly bound divalent counterions at low field strengths is supposed to reduce their contrib ution in the low-frequency effect in comparison to the effect from the less bound monovalent counterions. (C) 1997 Academic Press.