15.5 Interfacial Compartment Assembly

Interfacial Compartment Assembly describes the family of compartment formation processes that build a boundary structure at the interface between two immiscible liquid phases, rather than through bulk self-assembly of dispersed molecules in a single solvent. This pathway underlies the formation of emulsion droplets, particle-stabilized interfaces, and interfacially formed polymer or protein boundaries, all of which rely on the physical presence of a liquid-liquid interface as the site where boundary organization occurs.

Establishing the Interface

Water-Oil Interface Formation

Water-oil interface formation is the creation of a boundary region between an aqueous phase and an immiscible oil phase, arising from the two liquids' inability to mix, and providing the physical location at which subsequent boundary organization will take place.

Boundary Molecule Interfacial Adsorption

Boundary molecule interfacial adsorption is the accumulation of boundary-forming molecules, such as surfactants, polymers, or proteins, specifically at the water-oil interface rather than remaining dispersed within either bulk phase, driven by the favorable reduction in interfacial energy that adsorption provides.

Interfacial Monolayer Establishment

Interfacial monolayer establishment is the organization of adsorbed boundary molecules into a single, continuous layer along the interface, representing an intermediate structural stage that can either remain as a simple stabilized droplet boundary or serve as a precursor to a more elaborate boundary structure.

Droplet Formation Routes

Stabilized Aqueous Droplet Formation

Stabilized aqueous droplet formation is the process by which an aqueous phase is dispersed into discrete droplets within a surrounding oil phase, with the established interfacial monolayer preventing the droplets from immediately recombining.

Emulsion Transfer Compartment Assembly

Emulsion transfer compartment assembly is the pathway in which a lipid-stabilized aqueous droplet, formed within an oil phase, is transferred across a second lipid-coated interface into a bulk aqueous phase, converting the droplet into a fully aqueous-external lipid vesicle.

Phase-Transfer Boundary Completion

Phase-transfer boundary completion is the final structural step of emulsion transfer assembly, in which the droplet passing through the second interface acquires an additional boundary layer, completing a bilayer-like structure as it enters the external aqueous phase.

Double-Emulsion Compartment Assembly

Double-emulsion compartment assembly is the pathway in which an aqueous droplet is first enclosed within an oil droplet, which is itself then dispersed within a second, outer aqueous phase, producing a nested water-in-oil-in-water structure whose innermost aqueous droplet is separated from the outer aqueous phase by an intervening oil layer.

Alternative Boundary Materials at the Interface

Interfacial Polymer Membrane Formation

Interfacial polymer membrane formation is the organization of polymer chains adsorbed at a liquid-liquid interface into a continuous membrane-like layer, providing a route to a polymersome-like boundary structure built directly at the interface rather than through bulk copolymer self-assembly.

Interfacial Protein Boundary Formation

Interfacial protein boundary formation is the organization of protein molecules adsorbed at a liquid-liquid interface into a continuous, membrane-like boundary layer, representing the interfacial assembly route to a proteinosome-type structure.

Particle-Stabilized Interface Assembly

Particle-stabilized interface assembly is the process by which solid particles adsorb and pack together at a liquid-liquid interface, forming a mechanically reinforced boundary layer rather than a continuous molecular film, providing the assembly route to colloidosome-type structures.

Structural and Compositional Consequences

Interfacial Boundary Asymmetry

Interfacial boundary asymmetry refers to a compositional or structural difference between the two faces of an interfacially formed boundary, arising naturally from the fact that the boundary forms between two chemically distinct phases rather than within a single homogeneous solvent.

Organic Phase Removal

Organic phase removal is the process of eliminating the oil or other organic phase used during interfacial assembly once the boundary structure has formed, a step required to isolate the finished compartment in a purely aqueous external environment.

Interfacial Assembly Residual Solvent Burden

Interfacial assembly residual solvent burden refers to the possibility that traces of the organic phase or other interfacially involved solvents remain associated with the finished compartment even after organic phase removal, representing an unintended compositional consequence of the interfacial assembly route.

Endpoint of the Process

Interfacial Assembly Completion

Interfacial assembly completion is the point at which the boundary structure formed at the interface has become a stable, self-contained compartment capable of existing independently of the original interfacial conditions under which it formed, marking the conclusion of the interfacial assembly process.