pH-Responsive Gas Marbles Stabilized with Polymer Particles Carrying a Polyacid Steric Stabilizer

Gas marbles are particle-stabilized soft dispersed systems consisting of a soap-bubble-like air-in-water-in-air architecture. Herein, we report gas marbles stabilized by polystyrene particles carrying poly(acrylic acid) (PAA) steric stabilizers, which impart alkaline-responsive behavior to the assemblies. Unlike liquid marbles prepared from the same particles, the gas marbles could be fabricated over a broad size range while maintaining an almost perfectly spherical shape. They also exhibited remarkable stability on aqueous surfaces under acidic and neutral conditions, whereas exposure to alkaline solutions induced rapid disruption and release of the encapsulated gas owing to deprotonation of the surface-grafted PAA chains. In addition, the lifetime of the gas marbles was found to be strongly governed by evaporation of the thin water layer surrounding the gas core. Increasing the ambient relative humidity prolonged the lifetime from only a few tens of minutes at a relative humidity below 40% to more than 7 days above 70%. Furthermore, the gas marbles exhibited amphibious motion, allowing repeated transfer between air-water and air-solid interfaces while maintaining their integrity. These findings demonstrate that interfacial particle design and environmental conditions provide effective means of controlling gas-marble stability and responsiveness, establishing a basis for future studies on gas encapsulation, transport, and triggered release.