Particle‐Stabilized Materials: Dry Oils and (Polymerized) Non‐Aqueous Foams

Oil (liquids with low surface tension and practically immiscible with water) drops can be dispersed in air if relatively oleophobic particles are available. However, such particles with oil‐repellent surfaces cannot simply be prepared by controlling the particle surface chemistry alone. Herein the preparation of oil‐in‐air materials (oil marbles, dry oils) by changing the wetting behavior of particles by tuning the oil properties, which allows the formation of the metastable Cassie–Baxter wetting state of particle assemblies on oil drop surfaces, is presented. The oil‐in‐air materials can be converted to air‐in‐oil materials (non‐aqueous foams) by tailoring the oil properties, as the robustness of the metastable Cassie–Baxter state of the particle assemblies critically depends on the particle wettability. This conversion implies the phase inversion of dispersed systems consisting of air and oils. It is also shown that particle‐stabilized non‐aqueous foams can be utilized as template to produce macroporous polymers.