Tuning interfacial complexation in aqueous two phase systems with polyelectrolytes and nanoparticles for compound all water emulsion bodies (AWE-somes)

Interfacial complexation between two oppositely charged polymers in aqueous two phase systems (ATPSs) leads to the formation of mechanically robust microcapsules that can be stressed without losing their structural integrity. When a polyelectrolyte (PE) is replaced with a charged nanoparticle (NP), microcapsules with internal compartments can be generated within an encapsulated shell comprising NPs and PEs, named AWE-somes. These shells, made by interfacial complexation between PEs and NPs, are, however, very brittle and can lose their integrity under mechanical stress, potentially limiting their applications. Improved control over the properties and structure of microcapsules over a wide range is needed to enable their broad utilization. In this work, we show that interfacial complexation of a polycation with a mixture of a polyanion and a negatively charged NP in ATPS presents a simple yet versatile method of tuning the structure and properties of microcapsules. We show that internal structure, along with the mechanical robustness and stimuli-responsive properties of microcapsules, can be varied by changing the concentrations of polyanion and NP present in one of the two aqueous phases. Interfacial complexation of PE with mixtures of PE and NP provides a new strategy for controlling and imparting the properties and functionality of AWE-some interfacial membranes for applications in encapsulation and release of active agents and recapitulation of basic functions of living cells.