ELECTRIC BIREFRINGENCE STUDY OF THE DIELECTRIC-PROPERTIES OF ANISOTROPIC AND ELECTRICALLY CHARGED LATEX-PARTICLES

Static and dynamic electric birefringence measurements are performed o n aqueous dispersions of electrically charged fluorinated latex partic les having an almost spherical shape. The Kerr constant is nonzero bec ause of the intrinsic and form anisotropy of the particles, and is con siderably enhanced at low frequencies by a contribution due to the clo ud of dissociated counterions. We discuss in detail this effect which shows a non-Lorentzian frequency dispersion, and an amplitude strongly dependent on the particle concentration and on the ionic strength. Th e data are interpreted by making a connection with the theory of the d ielectric constant of polyelectrolyte solutions.