Structural Evolution and Formation Kinetics of Polyelectrolyte Complex Micelles

Polyelectrolyte complex (PEC) micelles form when oppositely charged block polyelectrolytes are mixed together in aqueous media. The polyelectrolyte blocks, driven by electrostatic interaction, associate and phase separate, leading to a dense, polymer-rich PEC core stabilized by a neutral block corona. These nanoscale PEC micelles have various biomedical applications including RNA therapeutic delivery, tissue engineering, and diagnostics. The formation kinetics of PEC micelles, however, remains unknown. We employ time-resolved SAXS to investigate the formation kinetics of PEC micelles and the effects of various parameters on the growth rate. We focus on a model polyelectrolyte system that we have expertise in synthesis and has been extensively studied: poly(ethylene oxide)-block-poly(vinyl benzyl trimethyl ammonium chloride) (PEO-b-PVBTMA) complexed with either poly(ethylene oxide)-block-poly(styrene sulfonate sodium) (PEO-b-PSSNa) or poly(acrylic acid sodium) PAANa. Achieving a nanoscale description of the growth kinetics via TR-SAXS experiments will contribute towards enhancing our understanding of the complexation-driven assembly processes, and allow better design of polyelectrolyte complex based materials for biomedical applications.