Interfacial rheology insights: particle texture and Pickering foam stability

Interfacial rheology studies were conducted to establish a connection between the rheological characteristics of particle-laden interfaces and the stability of Pickering foams. The behavior of foams stabilized with fumed and spherical colloidal silica particles was investigated, focusing on foam properties such as bubble microstructure and liquid content. Compared to a sodium dodecyl sulfate-stabilized foam, Pickering foams exhibited a notable reduction in bubble coarsening. Drop shape tensiometry measurements on particle-coated interfaces indicated that the Gibbs stability criterion was satisfied for both particle types at various surface coverages, supporting the observed arrested bubble coarsening in particle-stabilized foams. However, although the overall foam height was similar for both particle types, foams stabilized with fumed silica particles demonstrated a higher resistance to liquid drainage. This difference was attributed to the higher yield strain of interfacial networks formed by fumed silica particles, as compared to those formed by spherical colloidal particles at similar surface pressures. Our findings highlight that while both particles can generate long-lasting foams, the resulting Pickering foams may exhibit variations in microstructure, liquid content, and resistance to destabilization mechanisms, stemming from the respective interfacial rheological properties in each case.