Skip to main content

Research Repository

Advanced Search

Inversion of 'dry water' to aqueous foam on addition of surfactant

Johnson, Andrew J.; Rodrigues, Jhonny A.; Binks, Bernard P.


Andrew J. Johnson

Jhonny A. Rodrigues


Addition of charged surfactant to mixtures of air, water and hydrophobic silica nanoparticles under high shear induces transitional phase inversion from a water-in-air powder to an air-in-water foam. Optical and electron microscopy reveal the non-spherical shape of both drops and bubbles, respectively, in these materials due to their partial coverage by particles. Complementary experiments are described to elucidate the origin of phase inversion. From surface tension and contact angle measurements, the ratio of adsorption of surfactant at air-water and solid-water interfaces is determined. Particles become increasingly hydrophilic on adding surfactant since molecules adsorb tail down exposing charged head groups to the aqueous phase. The increased particle dispersibility into water and the generation of negative zeta potentials confirm this scenario. In addition, the ability of the same silica nanoparticles to act as antifoams of aqueous surfactant foams formed under low shear is investigated. The effectiveness of these particles as antifoams decreases both on increasing the surfactant concentration and the time particles and surfactant are in contact before foaming. Both trends are in agreement with the above-mentioned findings that when particles are rendered more hydrophilic via surfactant adsorption, they no longer break foam films between bubbles but remain dispersed in the aqueous phase.


Johnson, A. J., Rodrigues, J. A., & Binks, B. P. (2010). Inversion of 'dry water' to aqueous foam on addition of surfactant. Soft matter, 6(1), 126-135.

Journal Article Type Article
Acceptance Date Aug 21, 2009
Online Publication Date Oct 14, 2009
Publication Date 2010
Print ISSN 1744-683X
Electronic ISSN 1744-6848
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 6
Issue 1
Pages 126-135
Keywords General Chemistry; Condensed Matter Physics
Public URL