Stability and some properties of the second black film

Jones, Malcolm N.; Mysels, Karol J.; Scholten, P. C.

doi:10.1039/tf9666201336

Cited by 112 publications

(59 citation statements)

References 3 publications

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“…32 The dependence of γ (h; ) with h (see Fig. 8) agrees with the DLVO theory, 5,6 which considers a balance of electrostatic repulsion between the two layers and their effective attraction due to van der Waal forces. That theory explains the influence of salt concentration on the barrier height γ .…”

Section: Wetting Transition Theory and Newton Black Film Formationsupporting

confidence: 62%

“…Common black films (CBFs) have a thickness h > 5 nm, which varies with the ionic strength of the solution as predicted by the Poisson-Boltzmann theory (PBT). 5,6 For smaller thicknesses experimental and theoretical studies have reported significant deviations from the PBT. 7,8 At high salt concentration and low temperatures, CBFs undergo a transition to a thinner Newton black film (NBF) that is stable in the absence of external disturbances, and its thickness (h ≈ 3-4 nm) is almost insensitive to the amount of salt, temperature, or pressure.…”

Section: Introductionmentioning

confidence: 99%

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Newton black films as wetting systems

et al. 2012

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Newton black films (NBFs) can appear under a wide range of experimental conditions. NBFs define the adhesive states of foams and emulsions, showing their formation is a very general physical phenomenon. We show that the existence of NBFs and their whole experimental behavior can be understood within the theory of wetting transitions. NBFs are experimental realizations of partial wetting or pre-wetting states. Hence, they provide experimental systems to investigate the pre-wetting transition, and the spreading behavior under conditions that are very difficult to realize in other experimental systems. We also introduce two new computational approaches to obtain the disjoining pressure isotherm from canonical simulations, and to estimate the contact angles of droplets of nanoscopic dimensions.

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Section: Wetting Transition Theory and Newton Black Film Formationsupporting

confidence: 62%

Section: Introductionmentioning

confidence: 99%

Newton black films as wetting systems

et al. 2012

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“…The dependence of the common black film thickness with salt concentration is well described by the Poisson-Boltzmann theory. 3,[6][7][8] Significant departures from this theory have been found in NBFs though, 9 indicating a breakdown of the double layer picture in these thin films. Computer simulations of ionic NBFs have also shown that water is strongly polarized inside the films, showing that water cannot be modeled as a dielectric continuum with a pre-defined dielectric constant.…”

Section: Introductionmentioning

confidence: 98%

Adhesive transitions in Newton black films: A computer simulation study

Bresme

Chacón

Martínez

et al. 2011

The Journal of Chemical Physics

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We report molecular dynamics simulations of Newton black films (NBFs), ultra thin films of aqueous solutions stabilized with two monolayers of ionic surfactants, sodium dodecyl sulfate. We show that at low water content conditions and areas per surfactant corresponding to experimental estimates in NBFs, homogeneous films undergo an adhesion "transition," which results in a very thin adhesive film coexisting with a thicker film. We identify the adhesive film with the equilibrium structure of the Newton black film. We provide here a direct microscopic view of the formation of these important structures, which have been observed in experimental studies of emulsions and foams. We also report a detailed investigation of the structural properties and interfacial fluctuation spectrum of the adhesive film. Our analysis relies on the definition of an "intrinsic surface," which is used to remove the averaging effect that the capillary waves have on the film properties.

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“…Consequently, it is necessary to determine the details of the structure of NBF. Pioneering attempts have been made to do this using such experimental approaches as thin-film pressure balance, 12 optical measurement, 13 X-ray reflectivity, 14 FTIR, 15 and gas permeability. 16 Unfortunately, there remain considerable questions about the structure and properties of NBF.…”

Section: Introductionmentioning

confidence: 99%

Structures and Properties of Newton Black Films Characterized Using Molecular Dynamics Simulations

2006

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We used molecular dynamics (MD) simulations to investigate the structures and properties of Newton black films (NBF) for several surfactants: sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (C16TAB), and surfactin using film thicknesses up to 10 nm. By calculating the interface formation energy for various packing conditions on the surface pressure-area isotherm, we found that the most probable surface concentration is ∼42 Å 2 /molecule for SDS and C16TAB and ∼170 Å 2 /molecule for surfactin. We then used this most probable concentration of each surfactant to simulate NBF with various film thicknesses. From analyzing the disjoining pressure-film thickness isotherms with the density profiles and the solvation coordination number, we found that the increase of the disjoining pressure during the film thinning was coupled with the change in inner structure of the NBF (i.e., density profile and the solvation of ionic entities). In the range of film thicknesses less than ∼30 Å, the disjoining pressures for the SDS and C16TAB were found to be larger than that of the surfactin. We predicted the Gibbs elasticity (175 dyn/cm for surfactin; 109 dyn/cm for C16TAB; 38 dyn/cm for SDS) required to assess the stability of NBF against surface concentration fluctuations, and the shear modulus (6.5 GPa for the surfactin; 6.1 GPa for the C16TAB; 3.5 GPa for the SDS) and the yield stress (∼0.8 GPa for surfactin; ∼0.8 GPa for C16TAB; ∼0.4 GPa for the SDS) to assess the mechanical stability against the externally imposed mechanical perturbation.

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Stability and some properties of the second black film

Cited by 112 publications

References 3 publications

Newton black films as wetting systems

Newton black films as wetting systems

Adhesive transitions in Newton black films: A computer simulation study

Structures and Properties of Newton Black Films Characterized Using Molecular Dynamics Simulations

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