STATIC AND DYNAMIC LIGHT-SCATTERING OF COLLOIDAL CRYSTALS OF MONODISPERSED POLYSTYRENE SPHERES

Static and dynamic light-scattering measurements are made for colloida l-crystals, -liquids and -gases of monodispersed polystyrene spheres, 109 nm in diameter, in the exhaustively, deionized suspension and in t he presence of sodium chloride. Sharp peaks in the scattering curve ar e observed for the colloidal crystals in very diluted aqueous suspensi on. The product of the effective diffusion coefficient and the scatter ed light intensity is found constant over the whole range of the scatt ering angle measured for the colloidal crystals. Three and two dynamic processes have been extracted separately from time profiles of autoco rrelation functions of colloidal crystals and liquids, respectively fr om the non-negative least square analysis. Decay curves of colloidal g ases are characterized by a single translational diffusion coefficient , D-0. D-0 of the gases at low ionic concentrations is lower than the calculation (D-c) from the Stokes-Einstein equation with the true diam eter of spheres, and increases and reaches D-c as ionic concentration increases. These experimental results emphasize the important role of the expanded electrical double layers on the diffusive properties in t he colloidal crystals, liquids and gases.