Interaction forces between bubbles in the presence of novel responsive peptide surfactants
Thakshila S Balasuriya1, Raymond R Dagastine
1The Department of Chemical & Biomolecular Engineering, The Particulate Fluids Processing Centre, The University of Melbourne, Parkville, Victoria 3010, Australia.
Abstract:
Reversibly switchable surfactants are increasingly important for controlling foam stability in many industrial applications because they can be recycled as foaming and antifoaming agents. Novel stimuli responsive peptide surfactants have been previously studied to classify the molecular conformation at the air-water interface before and after switching. In this study, Atomic Force Microscopy (AFM) was used to correlate the peptide conformation to directly measured changes in colloidal interaction forces between immobilized air bubbles before and after switching. The surface tension values extracted from the AFM force measurements were compared to macroscopic pendant drop measurements to help elucidate the importance of desorption in the switching mechanisms for some of the peptides. Results were compared to previous studies of macroscopic foam-column stability using these peptides. Differences in foam stability and the AFM force measurements were apparent, highlighting variations in directly measured equilibrium colloidal interactions to macroscopic bulk behavior. These results help elucidate the connection between the switching mechanism of novel stimuli responsive peptide surfactants and their effect on colloidal scale interactions between bubbles.
Related Concept Videos
Surface Active Agents
Micelles
Colloids
Excess Pressure Inside a Drop and a Bubble
Surface Tension and Surface Energy
Consider a beaker filled with liquid. The bulk molecules in the liquid experience equal attractive forces on all sides with the surrounding molecules. However, the surface molecules experience a net attractive force downward due to the bulk molecules. The surface of the liquid behaves like a stretched membrane,...
Surface Tension, Capillary Action, and Viscosity
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...

