scholarly journals Foam film stratification studies probe intermicellar interactions

2021 ◽  
Vol 118 (25) ◽  
pp. e2024805118
Author(s):  
Chrystian Ochoa ◽  
Shang Gao ◽  
Samanvaya Srivastava ◽  
Vivek Sharma
Keyword(s):  
Surfactant Concentration ◽  
Debye Length ◽  
Step Size ◽  
Foam Films ◽  
X Ray Scattering ◽  
Air Interface ◽  
Micelle Size ◽  
Foam Film ◽  
Thickness Variations ◽  
Air Interfaces

Ultrathin foam films containing supramolecular structures like micelles in bulk and adsorbed surfactant at the liquid–air interface undergo drainage via stratification. At a fixed surfactant concentration, the stepwise decrease in the average film thickness of a stratifying micellar film yields a characteristic step size that also describes the quantized thickness difference between coexisting thick–thin flat regions. Even though many published studies claim that step size equals intermicellar distance obtained using scattering from bulk solutions, we found no reports of a direct comparison between the two length scales. It is well established that step size is inversely proportional to the cubic root of surfactant concentration but cannot be estimated by adding micelle size to Debye length, as the latter is inversely proportional to the square root of surfactant concentration. In this contribution, we contrast the step size obtained from analysis of nanoscopic thickness variations and transitions in stratifying foam films using Interferometry Digital Imaging Optical Microscopy (IDIOM) protocols, that we developed, with the intermicellar distance obtained using small-angle X-ray scattering. We find that stratification driven by the confinement-induced layering of micelles within the liquid–air interfaces of a foam film provides a sensitive probe of non-DLVO (Derjaguin–Landau–Verwey–Overbeek) supramolecular oscillatory structural forces and micellar interactions.

scholarly journals Interfacial Crystallization and Supramolecular Self-Assembly of Spider Silk Inspired Protein at the Water-Air Interface

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4239
Author(s):  
Pezhman Mohammadi ◽  
Fabian Zemke ◽  
Wolfgang Wagermaier ◽  
Markus B. Linder
Keyword(s):  
Self Assembly ◽  
Spider Silk ◽  
Assembly Process ◽  
Protein Solution ◽  
Time Resolved ◽  
Macromolecular Assembly ◽  
X Ray Scattering ◽  
Air Interface ◽  
Fundamental Research ◽  
Β Sheet

Macromolecular assembly into complex morphologies and architectural shapes is an area of fundamental research and technological innovation. In this work, we investigate the self-assembly process of recombinantly produced protein inspired by spider silk (spidroin). To elucidate the first steps of the assembly process, we examined highly concentrated and viscous pendant droplets of this protein in air. We show how the protein self-assembles and crystallizes at the water–air interface into a relatively thick and highly elastic skin. Using time-resolved in situ synchrotron X-ray scattering measurements during the drying process, we showed that the skin evolved to contain a high β-sheet amount over time. We also found that β-sheet formation strongly depended on protein concentration and relative humidity. These had a strong influence not only on the amount, but also on the ordering of these structures during the β-sheet formation process. We also showed how the skin around pendant droplets can serve as a reservoir for attaining liquid–liquid phase separation and coacervation from the dilute protein solution. Essentially, this study shows a new assembly route which could be optimized for the synthesis of new materials from a dilute protein solution and determine the properties of the final products.

scholarly journals Effect of surfactant redistribution on the flow and stability of foam films

2020 ◽  
Vol 476 (2234) ◽  
pp. 20190637
Author(s):  
Denny Vitasari ◽  
Simon Cox ◽  
Paul Grassia ◽  
Ruben Rosario
Keyword(s):  
Surface Tension ◽  
Channel Wall ◽  
Foam Stability ◽  
Intermediate Regime ◽  
Foam Films ◽  
Foam Film ◽  
Tension Increase ◽  
Constricted Channel ◽  
Film Tension ◽  
Foam Rheology

The viscous froth model for two-dimensional (2D) dissipative foam rheology is combined with Marangoni-driven surfactant redistribution on a foam film. The model is used to study the flow of a 2D foam system consisting of one bubble partially filling a constricted channel and a single spanning film connecting it to the opposite channel wall. Gradients of surface tension arising from film deformation induce tangential flow that redistributes surfactant along the film. This redistribution, and the consequent changes in film tension, inhibit the structure from undergoing a foam-destroying topological change in which the spanning film leaves the bubble behind; foam stability is thereby increased. The system’s behaviour is categorized by a Gibbs–Marangoni parameter, representing the ratio between the rate of motion in tangential and normal directions. Larger values of the Gibbs–Marangoni parameter induce greater variation in surface tension, increase the rate of surfactant redistribution and reduce the likelihood of topological changes. An intermediate regime is, however, identified in which the Gibbs–Marangoni parameter is large enough to create a significant gradient of surface tension but is not great enough to smooth out the flow-induced redistribution of surfactant entirely, resulting in non-monotonic variation in the bubble height, and hence in foam stability.

X-ray scattering by black foam films

1990 ◽  
Vol 268 (8) ◽  
pp. 760-765 ◽  
Author(s):  
D. Platikanov ◽  
H. Graf ◽  
A. Weiss
Keyword(s):  
X Ray ◽  
Foam Films ◽  
X Ray Scattering ◽  
Ray Scattering

scholarly journals Holes and cracks in rigid foam films

2015 ◽  
Vol 774 ◽  
Author(s):  
P. C. Petit ◽  
M. Le Merrer ◽  
A.-L. Biance
Keyword(s):  
Active Material ◽  
Surface Elasticity ◽  
Classical Problem ◽  
Film Rupture ◽  
Rigid Foam ◽  
Foam Films ◽  
Rupture Dynamics ◽  
Foam Film ◽  
Surface Active Material

The classical problem of foam film rupture dynamics has been investigated when the film interfaces exhibit very high rigidity due to the presence of specific surfactants. Two new features are reported. First, a strong deviation from the well-known Taylor–Culick law is observed. Second, crack-like patterns can be visualized in the film; these patterns are shown to appear at a well-defined film shrinkage. The key role of surface-active material on these features is quantitatively investigated, pointing to the importance of surface elasticity to describe these fast dynamical processes and thus providing an alternative tool to characterize surface elasticity in conditions extremely far from equilibrium. The origin of the cracks and their consequences on film rupturing dynamics are also discussed.

scholarly journals Charge fluctuation effects on the shape of flexible polyampholytes with applications to Intrinsically disordered proteins

2018 ◽  
Author(s):  
Himadri S. Samanta ◽  
Debayan Chakraborty ◽  
D. Thirumalai
Keyword(s):  
Electrostatic Interactions ◽  
Intrinsically Disordered Proteins ◽  
Debye Length ◽  
Disordered Proteins ◽  
Radius Of Gyration ◽  
Charge Fluctuation ◽  
Net Charge ◽  
Intrinsically Disordered ◽  
X Ray Scattering ◽  
Theoretical Predictions

Random polyampholytes (PAs) contain positively and negatively charged monomers that are distributed randomly along the polymer chain. The interaction between charges is assumed to be given by the Debye-Huckel potential. We show that the size of the PA is determined by an interplay between electrostatic interactions, giving rise to the polyelectrolyte (PE) effect due to net charge per monomer (σ), and an effective attractive PA interaction due to charge fluctuations, δσ. The interplay between these terms gives rise to non-monotonic dependence of the radius of gyration, Rg on the inverse Debye length, κ when PA effects are important . In the opposite limit, Rg decreases monotonically with increasing κ. Simulations of PA chains, using a charged bead-spring model, further corroborates our theoretical predictions. The simulations unambiguously show that conformational heterogeneity manifests itself among sequences that have identical PA parameters. A clear implication is that the phases of PA sequences, and by inference IDPs, cannot be determined using only the bare PA parameters (σ and δσ).The theory is used to calculate the changes in Rg on N, the number of residues for a set of Intrinsically Disordered Proteins (IDPs). For a certain class of IDPs, with N between 24 to 441, the size grows as Rg ~ N0.6, which agrees with data from Small Angle X-ray Scattering (SAXS) experiments.

scholarly journals Impact of Adsorption Layer Properties on Drainage Behavior of Microscopic Foam Films: The Case of Cationic/Nonionic Surfactant Mixtures

2020 ◽  
Vol 4 (4) ◽  
pp. 53
Author(s):  
Dimi Arabadzhieva ◽  
Plamen Tchoukov ◽  
Elena Mileva
Keyword(s):  
Surface Tension ◽  
Adsorption Layer ◽  
Thin Liquid Film ◽  
Fine Tuning ◽  
Molar Ratio ◽  
Clear Correlation ◽  
Surfactant Mixtures ◽  
Foam Films ◽  
Foam Film ◽  
Surfactant Systems

Aqueous mixtures of cationic hexadecyltrimethylammonium chloride (CTAC) and nonionic pentaethyleneglycol monododecyl ether (C12E5) are investigated. Adsorption layer properties are systematically studied within a wide concentration range for a 1:1 molar ratio of the surfactants. Surface tension and dilatational rheology measurements are conducted by profile analysis tensiometry. The interfacial data are juxtaposed to drainage kinetics and stability results for microscopic foam films, investigated by microinterferometric thin liquid film instrumentation. The obtained results give experimental evidence of synergistic interactions in the studied solutions, as compared to the corresponding single surfactant systems. Specific runs of dynamic and equilibrium surface tension curves are registered against the total surfactant quantity; the surface dilatational elasticities for the mixtures are systematically higher. A clear correlation is established between adsorption layer performance and foam film characteristics. The maxima of the film lifetimes are well outlined, and the respective values are shifted towards lower overall concentrations. The reported results substantiate the key role of the adsorption layers, and the surface dilatational properties in particular, for foam film drainage kinetics and stability. The well-expressed synergy observed in adsorption layer and foam film properties suggests the substantial benefits of using mixed surfactant systems in the design and fine-tuning of foam systems for innovative applications.

Effect of Acrylic Foam Film on Impact Reduction

2016 ◽  
Vol 715 ◽  
pp. 107-110
Author(s):  
Kyohei Takeo ◽  
Taichi Nogami ◽  
Tadaharu Adachi ◽  
Ryohei Koretoh ◽  
Hitoshi Tada
Keyword(s):  
Thin Films ◽  
Impact Load ◽  
Testing Machine ◽  
Research Impact ◽  
Foam Films ◽  
Impact Reduction ◽  
Foam Film ◽  
Reduction Effect ◽  
Falling Weight ◽  
The Impact

Recently, Thin Foam Films are Applied to Cushion Materials on Various Instruments, such as Mobile Phones, Tablet Computers, Etc. because of Reducing Load due to Drop Impact or Collision. Testing Methods of the Thin Films must Be Established to Estimate Effect of Thin Films on Reduction of the Impact Load. in this Research, Impact Reduction Effect of the Acrylic Foam Film with a Thickness below 1000μm was Clarified by Developing a Falling Weight Testing Machine. Maximum Value of the Impact Load Decreased Dominantly and the Plateau Region was Longer as the Thickness Increased. the Duration of the Load was Longer for the Thicker Film. Therefore, the Thin Acrylic Foam Films were Found to Be Effective in the Reduction of the Large Impact Load over 20 Kn.

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