title: Direct AFM force measurements between air bubbles in aqueous monodisperse sodium poly(styrene sulfonate) solutions.
abstract: Structural forces play an important role in the rheology, processing and stability of colloidal systems and complex fluids, with polyelectrolytes representing a key class of structuring colloids. Here, we explore the interactions between soft colloids, in the form of air bubbles, in solutions of monodisperse sodium poly(styrene sulfonate) as a model polyelectrolyte. It is found that by self-consistently modelling the force oscillations due to structuring of the polymer chains along with deformation of the bubbles, it is possible to precisely predict the interaction potential between approaching bubbles. In line with polyelectrolyte scaling theory, two distinct regimes of behaviour are seen, corresponding to dilute and semi-dilute polymer solutions. It is also seen that by blending monodisperse systems to give a bidisperse sample, the interaction forces between soft colloids can be controlled with a high degree of precision. At increasing bubble collision velocity, it is revealed that hydrodynamic flow overwhelms oscillatory structural interactions, showing the important disparity between equilibrium behaviour and dynamic interactions.
authors.affiliation: Particulate Fluids Processing Centre, The University of Melbourne, Parkville, Victoria 3010, Australia; School of Chemistry, The University of Melbourne, Parkville, Victoria 3010, Australia; Department of Chemical and Biomolecular Engineering, The University of Melbourne, Parkville, Victoria 3010, Australia. Electronic address: browneci@student.unimelb.edu.au.
authors.forename: Christine
authors.initials: C
authors.lastname: Browne
authors.affiliation: School of Chemistry, Monash University, Clayton, Victoria 3800, Australia. Electronic address: rico.tabor@monash.edu.
authors.forename: Rico F
authors.initials: RF
authors.lastname: Tabor
authors.affiliation: Particulate Fluids Processing Centre, The University of Melbourne, Parkville, Victoria 3010, Australia; School of Chemistry, The University of Melbourne, Parkville, Victoria 3010, Australia. Electronic address: franz@unimelb.edu.au.
authors.forename: Franz
authors.initials: F
authors.lastname: Grieser
authors.affiliation: Particulate Fluids Processing Centre, The University of Melbourne, Parkville, Victoria 3010, Australia; Department of Chemical and Biomolecular Engineering, The University of Melbourne, Parkville, Victoria 3010, Australia; Melbourne Centre for Nanofabrication, Clayton, Victoria 3168, Australia. Electronic address: rrd@unimelb.edu.au.
authors.forename: Raymond R
authors.initials: RR
authors.lastname: Dagastine
keywords: Atomic force microscope; Bubbles; Deformable; Monodisperse; Polyelectrolyte; Structural forces