Foaming Behavior of Polymer-Coated Colloids: The Need for Thick Liquid Films

Yu, Kai, Zhang, Huagui, Hodges, Chris, Biggs, Simon, Xu, Zhenghe, Cayre, Olivier J., and Harbottle, David (2017) Foaming Behavior of Polymer-Coated Colloids: The Need for Thick Liquid Films. Langmuir, 33 (26). pp. 6528-6539.

[img] PDF (Published Version) - Published Version
Restricted to Repository staff only

View at Publisher Website:


The current study examined the foaming behavior of poly(vinylpyrrolidone) (PVP)-silica composite nanoparticles. Individually, the two components, PVP and silica nanoparticles, exhibited very little potential to partition at the air-water interface, and as such, stable foams could not be generated. In contrast, combining the two components to form silica-PVP core-shell nanocomposites led to good "foamability" and long-term foam stability. Addition of an electrolyte (Na2SO4) was shown to have a marked effect on the foam stability. By varying the concentration of electrolyte between 0 and 0.55 M, three regions of foam stability were observed: rapid foam collapse at low electrolyte concentrations, delayed foam collapse at intermediate concentrations, and long-term stability (∼10 days) at the highest electrolyte concentration. The observed transitions in foam stability were better understood by studying the microstructure and physical and mechanical properties of the particle-laden interface. For rapidly collapsing foams the nanocomposite particles were weakly retained at the air-water interface. The interfaces in this case were characterized as being "liquid-like" and the foams collapsed within 100 min. At an intermediate electrolyte concentration (0.1 M), delayed foam collapse over ∼16 h was observed. The particle-laden interface was shown to be pseudo-solid-like as measured under shear and compression. The increased interfacial rigidity was attributed to adhesion between interpenetrating polymer layers. For the most stable foam (prepared in 0.55 M Na2SO4), the ratio of the viscoelastic moduli, G′/G″, was found to be equal to ∼3, confirming a strongly elastic interfacial layer. Using optical microscopy, enhanced foam stability was assessed and attributed to a change in the mechanism of foam collapse. Bubble-bubble coalescence was found to be significantly retarded by the aggregation of nanocomposite particles, with the long-term destabilization being recognized to result from bubble coarsening. For rapidly destabilizing foams, the contribution from bubble-bubble coalescence was shown to be more significant.

Item ID: 73348
Item Type: Article (Research - C1)
ISSN: 1520-5827
Copyright Information: © 2017 American Chemical Society
Date Deposited: 25 Aug 2022 00:35
FoR Codes: 34 CHEMICAL SCIENCES > 3406 Physical chemistry > 340603 Colloid and surface chemistry @ 100%
Downloads: Total: 3
More Statistics

Actions (Repository Staff Only)

Item Control Page Item Control Page