Studies of particle-particle interactions using polystyrene latices and time-average light scattering

Abstract

Dilute dispersions of monodisperse negatively-charged polystyrene latex particles, radii 161 A, have been examined by time-average light scattering at various latex volume fractions and electrolyte concentrations. The latter were varied from the low value produced by maintaining mixed bed ion-exchange resin beads in the systems (ca. 10-s tool dm -3) to the value of 5 • 10 -3 tool dm -3 obtained by the addition of sodium chloride. From angular scattering meastirements determinations of the structure factors were made; these were produced as a consequence of the particle-particle interactions in the system. By extrapolation of the structure factor to zero scattering angle, values were obtained for the osmotic compressibility and hence the osmotic pressure of the systems as a function of the latex volume fraction. It was found that the experimental data obtained could be interpreted in terms of a hard-sphere model for the particle-particle interaction. Good agreement was obtained provided that the particles were assigned a hard-sphere radius which was determined by the electrostatic repulsion between the particles.

Determination of size and effective surface charge of polystyrene latex particles in concentrated dispersion by SANS

“…The effective charge parameter, Z, however, appears to be only 6-7% of the total charge determined by surface titration. In addition, Z appears to increase with increase in volume fraction of the latex as observed by previous workers (Ottewill & Richardson, 1982).…”

“…Several techniques have been applied to obtain information on both structure and dynamics of such ordered latex particles in aqueous dispersion (Okubo, 1987;Hachisu & Kobayashi, 1974;Tomita & van de Ven, 1985;Schaefer & Ackerson, 1975;Ishii, Matsuoka & Ise, 1986;Cebula, Goodwin, Jeffrey, Ottewill, Parentich & Richardson, 1983). Use of liquid-state theories (Barker & Henderson, 1967) in the analysis of scattering data of latex dispersions has contributed a great deal to the understanding of interactions in concentrated dispersions (Cebula et al, 1983;Ottewill & Richardson, 1982). In these studies, the experimentally extracted structure factor, S(Q), was fitted to a hardsphere model with an effective radius determined by the particle size and the electrostatic double-layer repulsion.…”

Liquid‐liquid phase separations in aqueous solutions of globular proteins

“…These scattering data yield important information about the "structure," that is, correlations between the particles in charged colloidal dispersions, micellar solutions, and globular proteins (Ottewill and Richardson, 1982). An important quantity is the polyionpolyion structure factor S ( k ) :…”

“…For colloidal solutions, described by a one-component model [McMillan-Mayer approximation (Hansen and McDonald, 1986)], xT is an osmotic compressibility which can be determined: experimentally (Ottewill and Richardson, 1982). Utilizing angular light scattering (scattering angle 0 is proportional to the wave vector k ) , it is possible to obtain the structure factor S ( k ) (Ottewill and Richardson, 1982).…”

“…Interactions in colloidal dispersions are less complex than those in protein solutions; therefore, colloids may serve as model substances to test theoretical predictions for aqueous solutions of globular proteins. The one-component model applied in this work, frequently used to describe interactions in colloidal dispersions (Verwey and Overbeek, 1948; Asakura and Oosawa, 1958; Ottewill and Richardson, 1982;Cast et al, 1983; Crimson, 1983; Vincent and Hansen, 1984), may be useful for modeling aqueous solutions of globCorrespondence concerning this article should be addressed to 1. M. Prausnitz.…”