A molecularly informed field-theoretic study of the complexation of polycation PDADMA with mixed micelles of sodium dodecyl sulfate and ethoxylated surfactants

The self-assembly and phase separation of mixtures of polyelectrolytes and surfactants are important to a range of applications, from formulating personal care products to drug encapsulation. In contrast to systems of oppositely charged polyelectrolytes, in polyelectrolyte-surfactant systems the surfactants micellize into structures that are highly responsive to solution conditions. In this work, we examine how the morphology of micelles and degree of polyelectrolyte adsorption dynamically change upon varying the mixing ratio of charged and neutral surfactants. Specifically, we consider a solution of the cationic polyelectrolyte polydiallyldimethylammonium, anionic surfactant sodium dodecyl sulfate, neutral ethoxylated surfactants (CmEOn), sodium chloride salt, and water. To capture the chemical specificity of these species, we leverage recent developments in constructing molecularly informed field theories via coarse-graining from all-atom simulations. Our results show how changing the surfactant mixing ratios and the identity of the nonionic surfactant modulates micelle size and surface charge, and as a result dictates the degree of polyelectrolyte adsorption. These results are in semi-quantitative agreement with experimental observations on the same system.

Automated summary

This study examines the self-assembly and phase separation of polyelectrolyte-surfactant mixtures and their importance in various applications, such as personal care products and drug encapsulation. The researchers investigate how the morphology of micelles and degree of polyelectrolyte adsorption change with varying surfactant mixing ratios and the inclusion of nonionic surfactants. Using molecularly informed field theories constructed from all-atom simulations, they find that the size and surface charge of micelles can be modulated, affecting the degree of polyelectrolyte adsorption, which aligns with experimental observations.