MEASUREMENT OF ABSOLUTE COAGULATION RATE CONSTANTS FOR COLLOIDAL PARTICLES - COMPARISON OF SINGLE AND MULTIPARTICLE LIGHT-SCATTERING TECHNIQUES

The absolute coagulation rate constants of monodisperse spherical coll oids in aqueous suspension were measured at the early stage of the coa gulation processes by using two different techniques: single particle light scattering (SPLS) and simultaneous static and dynamic light scat tering (SLS + DLS), Single particle light scattering determines the cl uster-size distribution directly by counting the number of different c lusters during the coagulation process and therefore can be used to te st the kinetic growth model used for obtaining the coagulation rate co nstants, The simultaneous static and dynamic light-scattering method i s an in-situ experiment, where the average cluster size is estimated b y simultaneous static and dynamic lightscattering measurements at diff erent angles on a multiangle fiberoptics-based setup, A combined evalu ation of the static and dynamic light-scattering data permits the dete rmination of the absolute rate constants without the explicit use of l ight scattering form factors and hydrodynamic properties for dimers, I n this paper, we compare results obtained with both techniques, Good a greement was found for the absolute coagulation rate constants of two different latex particle suspensions, Furthermore, we show that the tw o techniques complement one another and the limitations of the first a re overcome by the second and vice versa. (C) 1997 Academic Press.