Interplay between autocatalysis and liquid-liquid phase separation produces hierarchical microcompartments

Our ability to synthesize life-inspired systems and materials is intimately connected to our understanding of the interplay between reactions, diffusion, phase separation, and self-assembly. The interaction between non-linear reactions (autocatalysis) and liquid-liquid phase separation is particularly interesting because of the emergence of functional properties and structures through instabilities, which are hard to predict theoretically without the help of experimental model systems. In this work, we studied systems where chemical autocatalysis is coupled to complex coacervation and the formation of oil-in-water droplets. The autocatalysis is driven by a nucleophilic chain reaction and is coupled to complex coacervation through the formation of tri- and tetracationic species. Interestingly, we observed the formation of hierarchical colloids when we used reactants that can form oil droplets in addition to coacervate droplets. This work illustrates a mechanism for the formation of complex, hierarchical microstructures by kinetically controlled self-assembly regulated by non-linear chemical reaction networks.