A new model to describe small‐angle neutron scattering from foams

• Published in: Journal of applied crystallography Vol. 55; no. 4; pp. 758 - 768
• Main Authors: Kühnhammer, Matthias, Braun, Larissa, Ludwig, Michael, Soltwedel, Olaf, Chiappisi, Leonardo, von Klitzing, Regine
• Format: Journal Article
• Language: English
• Published: 5 Abbey Square, Chester, Cheshire CH1 2HU, England International Union of Crystallography 01.08.2022; Blackwell Publishing Ltd
• Subjects: Drainage; Film thickness; foam films; Foams; Moisture content; neutron reflectometry; Neutron scattering; Neutrons; Polydispersity; Research Papers; small‐angle neutron scattering; Thin films; thin‐film pressure balances; Water content; small-angle neutron scattering; foam films; neutron reflectometry; foams; thin-film pressure balances
• ISSN: 1600-5767; 0021-8898; 1600-5767
• DOI: 10.1107/S1600576722004691

The modelling of scattering data from foams is very challenging due to the complex structure of foams and is therefore often reduced to the fitting of single peak positions or feature mimicking. This article presents a more elaborate model to describe the small‐angle neutron scattering (SANS) data from foams. The model takes into account the geometry of the foam bubbles and is based on an incoherent superposition of the reflectivity curves arising from the foam films and the small‐angle scattering (SAS) contribution from the plateau borders. The model is capable of describing the complete scattering curve of a foam stabilized by the standard cationic surfactant tetradecyltrimethylammonium bromide (C14TAB) with different water contents, i.e. different drainage states, and provides information on the thickness distribution of liquid films inside the foam. The mean film thickness decreases with decreasing water content because of drainage, from 28 to 22 nm, while the polydispersity increases. These results are in good agreement with the film thicknesses of individual horizontal foam films studied with a thin‐film pressure balance. A new model for the interpretation of small‐angle neutron scattering data from aqueous foams is presented and validated using experimental data from a model foam system.