Molecular Exchange Kinetics in Complex Coacervate Core Micelles

Complex coacervate core micelles (C3Ms) have been investigated in a wide range of applications owing to stimuli-responsiveness and hydrophilic cores. Compared to structure and morphology, much less is known about the kinetics of C3Ms, yet the fundamental understanding is essential for micelle stability, reproducibility, and stimuli-responsiveness. In this study, we investigated the equilibrium exchange dynamics of C3Ms characterized by time-resolved small-angle neutron scattering (TR-SANS). A pair of well-defined poly(ethylene oxide-b-allyl glycidyl ether) (PEO-PAGE) was synthesized and functionalized with charged moieties including guanidinium (G), ammonium (A), and sulfonate (S); one with a normal PEO, and the other with a fully deuterated PEO. C3Ms were prepared by simple mixing of two oppositely charged hPEO-PAGE (or dPEO-PAGE) solutions. Salt concentration dependence and polymer concentration dependence of the molecular exchange rate revealed that the coacervate core dynamics is crucial. Furthermore, a combination of the charged moieties significantly tunes the core dynamics, and thus the exchange rate.