(360a) Interfacial Activity of Silica and Ethyl Cellulose Particles in Fluid-Fluid Interfaces

Like surfactants, particles with appropriate wettability can adsorb at fluid-fluid interfaces. However, there has been a long-standing debate on whether particles can lower the interfacial tension in the same fashion as surfactants do. In our work, we used the pendant drop method to investigate the interfacial activity of isotropic silica nanoparticles at air-water and hexadecane-water interfaces and of ethyl cellulose particles at the trimethylolpropane trimethacrylate (TMPTMA)-water interface. Our results suggest that simple, non-amphiphilic particles can change the interfacial tension as long as they do adsorb (make physical contact with the interface) and have strong affinity to the interface (high desorption energy). We also proposed a simple model that does not explicitly account for any particle-particle interaction but is seen to predict surprisingly well the effective interfacial tension due to particle adsorption at fluid-fluid interfaces. Our work also provides a convenient way to estimate the packing density of particles in fluid-fluid interfaces by combining dynamic interfacial tension measurements with information about the particles’ wetting properties.