Molecular Exchange Kinetics in Complex Coacervate Core Micelles: Role of Associative Interaction

Abstract

Molecular exchange dynamics between spherical complex coacervate core micelles (C3Ms) are documented using time-resolved small-angle neutron scattering measurements (TR-SANS), and the effects of salt concentration, type of charges, and core block polydispersity to the chain exchange are quantified. Isotopically labeled block copolyelectrolytes were prepared by postpolymerization modification of two nearly identical poly­(ethylene oxide-b-allyl glycidyl ether), one with normal and the other with deuterated PEO blocks (i.e., hPEO–PAGE and dPEO–PAGE). The observed rates at multiple salt concentrations are consolidated using time-salt superposition shift factors representing chain exchange rates and analyzed. Our comprehensive analytical relaxation function based on the sticky-Rouse model and the thermodynamic barrier for core block extraction successfully describes the molecular exchange kinetics between the isotopically labeled C3Ms. We believe this work provides fundamental design criteria for C3Ms with engineered chain exchange dynamics.

DNA dynamics in complex coacervate droplets and micelles

“…These differences between C3Ms and amphiphilic diblock copolymer micelles can explain why we could not use the amphiphilic diblock copolymer model to describe the exchange of PSPMA/PEG–PTMAEMA micelles 22 and why in a recent SANS study of C3M exchange a lower polydispersity was needed than measured to obtain a good fit between the exchange data and the amphiphilic diblock copolymer model. 24 Furthermore, these differences stress the importance of specifically studying C3Ms to further unravel the effect of chain lengths and other parameters on the C3M exchange rate.…”

“…Recently, the molecular exchange of C3Ms was also measured by small angle neutron scattering (SANS) and also here the presence of different exchange rates was explained by chain polydispersity. 24 However, this polydispersity hypothesis has not been confirmed yet, since so far only the exchange of polydisperse polymers has been measured. Measuring the exchange of C3Ms with ssDNA allows to thoroughly test this hypothesis because the DNA is monodisperse and its length can be systematically varied.…”

Ionic group-dependent structure of complex coacervate hydrogels formed by ABA triblock copolymers

“…Previous works, including our efforts, have found that polyguanidines are less hydrated and result in stronger ion-pair interactions with anionic polyelectrolytes than polyamines. 22–25 Therefore, as the guanidinium fraction in the cationic end-block increases, we anticipate stronger segregation of the coacervate cores and enhanced gel stability against the addition of external salt, called “salt resistance.” The nanostructures and water content in the coacervate cores as functions of guanidinium fraction and salt concentration were characterized by small-angle X-ray and neutron scattering (SAX/NS). These structural features were further utilized to assess the interfacial tension at the zero-salt limit and the salt resistance of the coacervate core based on the scaling description.…”

Amphiphilic Random-Block Copolymer Micelles in Water: Precise and Dynamic Self-Assembly Controlled by Random Copolymer Association

“…As a result, the aggregation number ( N agg ) is also controllable by the DP. Block copolymer micelles are often kinetically frozen in pure water at ambient temperature, except for specific conditions (e.g., in organic solvent/water mixtures at high temperature), − because of the strong association of highly hydrophobic polymer chains in the cores and/or high glass-transition temperature of the polymer chains. However, amphiphilic random copolymers, as well as surfactants and small amphiphiles, − afford polymer chain exchange between micelles in water even at room temperature .…”