Scalable Manufacturing of Hierarchical Biphasic Bicontinuous Structures via Vaporization-Induced Phase Separation (VIPS)

Studies of particle-stabilized biphasic structures have greatly expanded the possibilities of multiphasic systems by producing liquid composites with unique morphologies and properties. The solvent transfer-induced phase separation (STRIPS) method was previously introduced to prepare bicontinuous interfacially jammed emulsion gels (bijels), a unique class of particle-stabilized biphasic structures. Although STRIPS enables continuous processing, the requirement of an external aqueous phase may limit its application. In this work, a new method to produce a variety of three-dimensional multiphasic structures including bijels via vapor-induced phase separation (VIPS) is demonstrated. VIPS enables the fabrication of films and coatings by spreading or spraying a particle-laden suspension onto a surface without the need of an outer aqueous phase. Intriguingly, secondary nucleation of structures occurs within phase separated domains, leading to hierarchically bicontinuous biphasic structures. The dimensions of phase separated domains can be controlled by the rate of cosolvent removal. Moreover, a different path to bicontinuous morphology is identified, which does not occur via spinodal decomposition but rather relies on the formation of percolating structures of partially coalesced particle-covered droplets. The VIPS process provides a scalable path to produce bicontinuous biphasic composites with hierarchical structures for advanced coatings and membranes applications.