Abstract
In this work we present a simple model for the kinetics of agglomeration and aggregation of colloidal particles. We consider that particles agglomerate rapidly and endothermically forming oligomers. These oligomers can, in turn, aggregate irreversibly, in a process that leads to the destabilization of the colloidal system. As these two processes have very different relative energy activations, they occur in different time-scales: the first step is faster and reaches a state of quasi‑equilibrium. Because of this, the enthalpy change during the agglomeration can be experimentally determined through the variable temperature multiple light scattering (VTMLS) method. Interestingly, this value is related to the relative kinetic stability of the system and can be used to evaluate the stability of new colloidal compositions. Our results are in qualitative agreement with experimental data of low concentration colloidal dispersions consisted of polymer particles and/or surfactant-coated particles.
Highlights
Colloidal dispersions are composed of microscopic solids suspended in a fluid
In order to investigate the validity of the thermodynamic analysis on which the variable temperature multiple light scattering (VTMLS), a novel technique that allows rapid and non-destructive evaluation of the relative stability of colloidal dispersions, is based, we have modeled the kinetics involved
We have developed a simple model for kinetic reversible agglomeration followed by irreversible aggregation of colloidal particles, for polymer particles and/or surfactant-coated particles at low concentrations
Summary
Colloidal dispersions are composed of microscopic solids suspended in a fluid. These systems occur naturally in many situations in biological processes and have an ever growing importance in many realms of technology and science, be it as drug carriers, paints and inks, selfassembling structures, or model systems for the study of collective behavior of crystal, glasses and gels.[1,2,3,4,5]Colloidal systems are, inherently thermodynamically unstable due to surface effects, as a single solid phase would have lower energy. It is possible for these systems to be kinetically stable, depending on its lifetime The control of such stability is of great importance in the development of colloidal dispersions for therapeutic uses.[6,7,8,9,10,11,12,13] A better understanding of the kinetics involved in the mechanisms of instability has been the aim of several studies since the early works from Smoluchowski[14] up to more recent and thorough approaches, which consider the influence of the secondary interaction energy minimum[15,16] a key feature for self-assembling systems
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