The interfacial structure of polymeric surfactant stabilised air-in-water foams

Article English OPEN
Hurcom, J. ; Paul, A. ; Heenan, R.K. ; Davies, A. ; Woodman, N. ; Schweins, R. ; Griffiths, P.C. (2014)
  • Publisher: Royal Society of Chemistry
  • Journal: Soft Matter, volume 10, pages 3,003-3,008
  • Related identifiers: doi: 10.1039/c3sm52877d
  • Subject: RS | QD

Small-angle neutron scattering was used to probe the interfacial structure of nitrogen-in-water foams created using a series of tri-block polymeric surfactants of the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (EOx-POy-EOx) range, from which the nature of the polymeric interface could be characterised. The data follow a pronounced Q(-4) decay, along with a number of inflexions and weak but well-defined peaks. These characteristics were well-described by a model embodying paracrystalline stacks of adsorbed polymer layers, whose formation is induced by the presence of the air-water interface, adsorbed at the flat air-water (film lamellae) interface. A minimum of approximately five paracrystalline polymer layers of thickness of the order of 85-160 Å, interspersed with somewhat thicker (400 Å) films of continuous aqueous phase were found to best fit the data. The thickness of the layer (L) was shown to follow a relationship predicted by anchor block dominated polymer adsorption theories from non-selective solvents, L ∼ EO(1)PO(1/3). The insight gained from these studies should permit a more rational design of polymeric stabilisers for hydrophilic polyurethane foams.
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