| Colloidal polyelectrolyte/counterion micro- and nanogels form automatically via ionic crosslinking, upon mixing multivalent counterions solution with dilute polyelectrolyte solution. Despite the broad application and abundant research of these colloidal materials, most of the studies have been based on trial and error without mechanistic understanding of their formation and coagulation process, and, the relation between molecular and colloidal interactions to their final properties (e.g., size distributions and stabilities). The lack of mechanistic understanding leads to poor control, reproducibility and explanation of experimental results. To address this, isothermal titration calorimetry (ITC) was first used to relate the binding thermogram to the formation and coagulation of polyelectrolyte/counterion colloidal particles. Chitosan/TPP micro- and nanogel system was then studied by ITC, dynamic light scattering (DLS), transmission electron microscopy, zeta-potential and stopped-flow light scattering under various conditions (i.e., pH and ionic strength) to probe the mechanism of the micro- and nanogel formation and coagulation, and, to relate the molecular/colloidal interactions to their final properties(e.g., size distributions and stabilities). |
