Kinetics of heterocoagulation. Part 4.—Evaluation of absolute coagulation rate constants using a classical light scattering technique

Abstract

The rate of coagulation in systems of identical and unlike colloids in aqueous media has been studied by a simultaneous multi-angle static light scattering technique. The mixed dispersions consisted of polystyrene latex particles of different radii and of opposite sign of charge. A procedure based on the Rayleigh-Gans-Debye approximation permits one to estimate the absolute rate constant either for homo-or hetero-coagulation. The absolute coagulation rate constants were compared to those calculated theoretically, using the Smoluchowski theory. In homosystems, the fast coagulation rate corresponded to ca. 5540% of the Smoluchowski value. In the heterosystem, the coagulation rates exceeded the calculated values based on the diffusion-controlled process at a low ionic strength. An increase in the electrolyte content led to a decrease of the coagulation rate, which at high concentrations corresponded to ca. 85% of the Smoluchowski value.

Measurement of Absolute Coagulation Rate Constants for Colloidal Particles: Comparison of Single and Multiparticle Light Scattering Techniques

“…Using this combined technique, neither any mation obtained for the time evolution of monomers and a priori knowledge of the light scattering power nor the dimers at short times (Eqs. [6] and [7]), one obtains a hydrodynamic properties of the dimers is required for delinear relationship between the initial slope of the scattered termining the coagulation rate constants. Thus, the combinalight intensity and the coagulation rate constant, tion of simultaneously performed static and dynamic light scattering measurements allows the absolute coagulation rate constant to be determined unequivocally.…”

“…[6] and [7] into Eq. [11] and expanding for short times, This coagulation half-time represents a useful time scale for the identification of the early stages in the coagulation 1…”

“…[6] namic radius at the early stages of coagulation is determined by the difference between the hydrodynamic radii of the [7] monomer and the dimer. The combination of Eq.…”

Agregación de sistemas coloidales con cargas opuestas: efecto de la concentración de partículas

“…Por tanto, en la expresión =0. Así pues, la dependencia de la pendiente inicial de la curva de intensidad dispersada frente al tiempo en la proporción relativa de partícu-las se simplifica [6]: (5) siendo n A =N A /N 0 . Por tanto, esperamos una dependencia parabólica con n A .…”

Stimulus-Responsive Heteroaggregation of Colloidal Dispersions: Reversible Systems and Composite Materials

“…The Rayleigh-Debye-Gans (RDG) approximation is usually applied to calculate the rate constant from light scattering. Ryde and Matijevic [9] have successfully explored RDG theory to support their light scattering data and reported that absolute heteroaggregation rate constants can be determined by analyzing time-dependent multi-angle static light scattering (SLS). Using the RDG theory, Galetto et al [10] have focused on the time resolved simultaneous static and dynamic light scattering (SSDLS) of larger and complex particles.…”