Mechanism of Dissociation Kinetics in Polyelectrolyte Complex Micelles

Polyelectrolyte-based nanoscale self-assemblies, such as micelles, possess diverse desirable attributes such as the capability for sequestering and protecting biomacromolecules against inhospitable environments, responsiveness to external stimuli, and tunability of physical behavior. However, little is known on the mechanisms of dissociation when micelles encounter and respond to environmental changes. Using salt-jump, time-dependent light scattering, the pathway of dissociation is observed in polyelectrolyte complex micelles that have complex cores and neutral coronas. The micelle dissociation kinetics appear to be a three-stage process, in good agreement with the scattering data. Using kinetic models of amphiphilic block copolymer micelles in polyelectrolyte complexation-driven micelles, we derive an analytical expression for dissociation relaxation rates as a function of solvent temperature, salt concentration, and the length of the charged polymer blocks. The theoretical predictions are compatible with the experimental data from light scattering experiments. This study experimentally demonstrates the relaxation kinetics of polyelectrolyte complex micelle dissociation and illustrates the underlying mechanism governing the dissociation kinetics. It is anticipated that these findings can be generalized to other electrostatic interaction-driven self-assemblies to better understand the relationship among the kinetics of dissociation, constituent polymer properties, and environmental parameters.