Supporting data for “Controlling the morphology of all-aqueous complex droplets”

Emulsions formed by liquid-liquid phase separation (LLPS) are central components of pharmaceutics, foods, cosmetics and functional soft materials. Complex emulsions, such as multiple (multilayered) emulsions or Janus emulsions formed by multiple phases possess more functionalities, such as controlled release and sensing. The properties and functions of complex emulsions are intimately related to their structures. For instance, layered emulsions are designed for controlled release, while Janus emulsions are optimal templates for targeted release. Thus, controlling the morphology of complex emulsions is very critical. Traditionally, the morphology of complex emulsion can be tuned by surfactants, as seen in oil-water systems, where dynamically reconfigurable complex emulsions have been realized by gradually varying the concentration of surfactants or designing stimuli-responsive surfactants. However, such surfactant-based approach is normally not effective in all-aqueous systems. This is because the all-aqueous droplets possess ultra-low interfacial tension (from 1 µN/m to 1 mN/m), which hinders the adsorption of general surfactant-like molecules at their interfaces. Depending on the interaction between molecules, all-aqueous complex droplets can be generated from both segregative and associative LLPS. A unique feature of all-aqueous complex droplets is their biocompatibility with biological components that is unattainable by traditional oil-water systems, making them ideal vehicles for macromolecules. Composition and temperature-dependent routes have been reported to shape certain all-aqueous multiphase droplets. For instance, the number of layer within an all-aqueous layered droplet can be altered by relative ratio of two segregative polymers. Nevertheless, a general strategy to achieve dynamic all-aqueous complex emulsions with different wetting configurations has yet to be realized.

In our work, we develop methods to controllably form all-aqueous complex emulsions under the ultra-low interfacial tension regime. To gain a comprehensive understanding and develop generic strategies for morphology control, all-aqueous complex droplets from different LLPS mechanisms, namely segregative and associative LLPS, are studied.