UCLA

Polyelectrolyte complex (PEC) coacervate dispersions are a versatile platform for the realization of aqueous colloidal encapsulants and bioreactors. The membraneless microdroplets comprising these dispersions form by liquid-liquid phase separation and introduce a distinct and unstable water-water interface with external aqueous environments, eventually leading to their coalescence and resulting in macro phase separation. This is a well-known phenomenon, that can be explained by conventional theories such as Voorn-Oberbeek (VO) model. Previously, we have shown that comb polyelectrolytes (cPEs) stabilize the coacervate microdroplets against coalescence, enabling the formulation of stable coacervate microemulsions. Stabilized PEC microdroplets possess unique properties like higher salt resistance, an expanded two-phase region, stable compartmentalization over longer periods of time, and higher stability under diverse conditions like (temperature, pH, ionic strength). However, predictions of phase separation and phase composition are a major challenge upon addition of cPEs in PEC systems. In this study, we have rigorously studied one widely used PE system constructed of poly(diallyldimethylammonium chloride) (PDADMAC) as a polycation and poly(acrylic acid) (PAA) as a polyanion, while negatively charged MasterGlenium 7500 served as a cPE. This fundamental study aims to quantify phase composition using a series of thermogravimetric analysis. Along with rheology and high throughput turbidimetry measurements proving robustness of this stabilization strategy. Resorting to recent microfluidics advancements, a strategy to form monodisperse microdroplets is also discussed here. Overall, the results presented here will provide crucial information enabling a wide range of applications such as tailoring protocells and microreactors.