Domain growth dynamics and local viscosity in stratifying foam films

Abstract

We present a quantitative theory and experiments for the expansion dynamics of domains in stratifying foam films. Foam films containing micelles, colloidal particles or polymer-surfactant complexes often form layered structures and thin in a stepwise fashion: circular domains of lower thickness are formed and expand following a R(t) proportional variant t1/2 law. In the present paper the film is modeled by an incompressible three-dimensional fluid with incompressible surfaces. The film tension difference between the film and domains results in the formation of a rim at the domain boundary and a gradient in film thickness and pressure in the surrounding film. The material transport due to this gradient lets the domains grow. We present experiments utilizing the thin balance method to qualitatively confirm the thinning mechanism and to determine material parameters including local film viscosity of a film composed of 4400 ppm acrylamide/acrylamidomethylpropanesulfonate-copolymer and 0.006 mmol/l dodecyltrimethylammonium bromide solution. We found a film viscosity of about 60 times the bulk viscosity, consistent with previous measurement in the same system but using another method.

Effect of polyelectrolytes on (de)stability of liquid foam films

“…This was found for C 12 TAB/PAMPS and C 12 TAB/CMC lms. 69,70 One reason for the decrease in Fig. 14 Disjoining pressure as a function of film thickness for APG/ PDADMAC films at two different degrees of PDADMAC charge: 100% (fully charged chain) and 24%. The graph is taken from.…”

Domain expansion dynamics in stratifying foam films: experiments

“…18,43 The latter forces can nearly counterbalance capillary pressure at substantially higher thicknesses (B80 nm) than DLVO forces (significant only below B40 nm). 42,44,[48][49][50] These are explored herein in the context of domain expansion dynamics. 43,44 While many studies have focused on the equilibrium state of each thickness step and its relation to supramolecular structural components of disjoining pressure, 43,[45][46][47] there are many unanswered questions regarding the physicochemical hydrodynamics underlying stratification.…”

Stratification Kinetics of Polyelectrolyte Solutions Confined in Thin Films

“…The relation between D and D w is nontrivial [16], but as D, D w is inversely proportional to the bulk viscosity . The local shear rate can be estimated as dr=dt=h and is of the order of 200 s ÿ1 .…”