Particle Size-Driven Transition from Multilayer Aggregates to Ordered Monolayers at Gas Marble Interfaces

Gas marbles (GMs) are a family of particle-stabilized soft dispersed systems with a soap bubble-like air-in-water-in-air structure. Here, we investigate the effect of the stabilizing particle size on the resulting structure and properties of GMs. We synthesize a series of polystyrene particles with diameters between 2 and 1050 μm by dispersion polymerization and seeded dispersion polymerization. We surface-modify these particles with a poly[2-(diethylamino)ethyl methacrylate] polymeric steric stabilizer to enable interfacial adsorption to the air/water interface. This set of particles enables us to form GMs and isolate the effect of particle size on the GM formation and stabilization efficiency. We find that particles with sizes ≥80 μm adsorb as a particle monolayer to the surface of the GM, while smaller particles adsorb as ill-defined, multilayered aggregates. These results indicate that the force balance between particle-particle interaction and gravity is an important parameter to control the surface structure of the GMs. Furthermore, the degree of hexagonal ordering increases monotonically with particle size, reflecting enhanced packing regularity for larger particles. The assembly structure and size of the particles also correlate with the mechanical integrity of the GMs against fall impact. The mechanical resistance is governed by the gap between the inner liquid of the GM and the supporting substrate, as well as by the associated potential energy, both of which depend on particle size. In summary, our study systematically explores structure-property-performance relationships connecting the stabilizing particle size with the interfacial structure and the resultant mechanical stability of the macroscopic GM.