| Abstract
| - We study the early stage coagulation kinetics for a charged colloidal dispersion which is here modeledby an effective two-body colloid−colloid potential. The colloidal system was physically prepared by choosingsets of colloidal parameters varying in particular the Hamaker constant and the particle's size. The kineticsof coagulation process was driven by the addition of an indifferent electrolyte and assumed to proceed intwo quasi-steady steps. In the first step, colloidal particles are destabilized by the presence of a secondpotential minimum to diffuse from a bulk-stabilized liquid phase to a flocculated phase. In the second step,we assume that different entities are found in the second potential minimum. The entities comprise secondarydimers, secondary dimers undergoing redispersion, and monomers still in singlet states. If, under favorablecondition, this kind of interaction-driven diffusive motion continues, a fraction of the secondary dimerswill be induced to undergo primary dimers formation in the first deep minimum. Whether or not the latterprocess occurs is determined either energetically by the potential barrier falling below a prescribed value,say of 15kBT, or/and the second potential minimum becoming negligibly small (with a magnitude <kBT).A prototype example to exhibit this kind of the coagulation kinetics phenomenon is an aqueous dispersionof polystyrene latex particles. Our detailed analysis on this system showed the connection between thechange of rate constants and the reversible flocculation⇄irreversible coagulation transition and wouldthrow a fresh light on the use of both the energy and the kinetic criteria for understanding the colloidalstability such as those observed in the liquid−liquid coexistence.
|
