Stability of aqueous foam films and foams containing polymers: Discrepancies between different length scales

Braun, Larissa; Kühnhammer, Matthias; Klitzing, Regine von

doi:10.1016/j.cocis.2020.08.004

Cited by 33 publications

(28 citation statements)

References 92 publications

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“…The traditional versions of the thin film balance usually study films at equilibrium, or quasi-static conditions, and often in a well-protected environment, conditions that are too ideal when compared to other experiments involving droplets or even emulsions Suja et al 2020). Thus, film properties do not always correlate well with the macroscopic properties of the material (Braun et al 2020;Monin et al 2000). In the present work, we study how pressure variations and the presence of extrinsic factors like impurities affect the dynamics and lifetimes of the freestanding films.…”

Section: Introductionmentioning

confidence: 93%

“…For example, the rheological properties of interfaces at the air/water interface are known to affect both drainage and Ostwald ripening (Saint-Jalmes 2006; Beltramo et al 2017;Georgieva et al 2009), which in turn influence the average bubble size, and thus the so-called yield stress, of the macroscopic foam (Princen and Kiss 1989;Kraynik and Hansen 1987). Nevertheless, comparison of the same system at different lengthscales (micro-and mesoscale) remains difficult (Rio and Biance 2014;Monin et al 2000;Braun et al 2020) and has so far been reported mainly at a qualitative level. Therefore, it is still unclear if experimental techniques with access to different lengthscales probe the same macroscopic properties.…”

Section: Introductionmentioning

confidence: 99%

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Studying coalescence at different lengthscales: from films to droplets

et al. 2022

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The hydrodynamics of thin films is an important factor when it comes to the stability and rheology of multiphasic materials, such as foams, emulsions, and polymer blends. However, there have so far been only limited experimental studies addressing the dynamics of individual free-standing thin films at conditions similar to those encountered on macroscopic scales. In this article, we study a well-characterized system of a water-in-oil emulsion stabilized by a non-ionic surfactant (SPAN80) close to its CMC. We employ a dynamic thin film balance, to study the dynamics of freestanding films under both constant and time-varied pressure drops. We compare with the recently published results of Narayan et al. (2020) on colliding droplets of the same system with a hydrodynamic microfluidic trap, and show for the first time that agreement between the two lengthscales is possible, which indicates that the coalescence is indeed dominated by the dynamics in the film. We then address the scatter in the coalescence times and show that it can be affected by extrinsic factors, as well as by variations in the collision angle. Finally, we discuss the difficulties of extracting insight on the coalescence mechanism from coalescence time distributions when different effects such as impurities, small pressure variations, collision angle variations, and possible Marangoni-related instabilities are at play.

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Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Studying coalescence at different lengthscales: from films to droplets

et al. 2022

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“…The reliable description of these two interrelated processes evokes hot topics of ongoing research, including film thinning in the presence of partially mobile interfaces, polymerization/cross-linking under soft confinement or the statistics of thermally initiated hole formation in a viscoelastic thin film. [16][17][18][19][20][21] Once ruptured locally, the equilibrium of interfacial and bulk-film stresses leads to a variety of possible hole openings in-between the extreme cases of a fully open or a fully closed film. A selection of characteristic morphologies is shown in Figure 1b.…”

Section: Introductionmentioning

confidence: 99%

Investigating Pore‐Opening of Hydrogel Foams at the Scale of Freestanding Thin Films

Andrieux

Patil

Jacomine

et al. 2022

Macromol. Rapid Commun.

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Controlling the pore connectivity of polymer foams is key for most of their applications, ranging from liquid uptake, mechanics, and acoustic/thermal insulation to tissue engineering. Despite their importance, the scientific phenomena governing the pore‐opening processes remain poorly understood, requiring tedious trial‐and‐error procedures for property optimization. This lack of understanding is partly explained by the high complexity of the different interrelated, multiscale processes which take place as the foam transforms from an initially fluid foam into a solid foam. To progress in this field, this work takes inspiration from long‐standing research on liquid foams and thin films to develop model experiments in a microfluidic “Thin Film Pressure Balance.” These experiments allow the investigation of isolated thin films under well‐controlled environmental conditions reproducing those arising within a foam undergoing cross‐linking and drying. Using the example of alginate hydrogel films, the evolution of isolated thin films undergoing gelation and drying is correlated with the evolution of the rheological properties of the same alginate solution in bulk. The overall approach is introduced and a first set of results is presented to propose a starting point for the phenomenological description of the different types of pore‐opening processes and the classification of the resulting pore‐opening types.

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“…This owes to the particle deformability which brings original properties at the interface compared to solid particles [2,3,4]. In particular, the adsorption of microgels at liquid interfaces has led to the stabilization of so-called Pickering emulsions and foams, which can be further destabilized on demand by triggering the volume phase transition of microgels from swollen to collapsed state [5][6][7][8][9][10][11][12][13]. To date, a great knowledge has been collected using poly(N-isopropylacrylamide) as model microgels [3,4,14].…”

Section: Introductionmentioning

confidence: 99%

Pickering emulsions stabilized by thermoresponsive oligo(ethylene glycol)-based microgels: Effect of temperature-sensitivity on emulsion stability

Tatry

Galanopoulo

Waldmann

et al. 2021

Journal of Colloid and Interface Science

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HypothesisThe stability of emulsions stabilized by soft and responsive microgels and their macroscopic properties are governed by the microstructure of microgels, in particular their deformability. However, little is known about the role of the microgel chemistry, though it is expected that polymeric backbone with an amphiphilic structure is a requirement for their adsorption at the oil-water interface. ExperimentsA series of biocompatible, thermoresponsive and amphiphilic poly(oligoethylene glycol)methacrylate (pOEMA) microgels is synthesized, with varying hydrophobic-hydrophilic balance, or equivalent varying volume phase transition temperature (VPTT). Their behavior in the bulk phase and at solid interfaces is compared to their behavior at liquid interfaces, studied on flat and model interfaces by the pendant drop method, and on drops, in microgel-stabilized emulsions. FindingsControlling the composition of microgels by simply changing the number of ethylene oxide groups in the hydrophilic side chain allows a precise tuning of their VPTT in the range of 20 to 60°C. Simultaneously, the swelling ratio and the deformability of the microgels increase by increasing the hydrophilicity, as a result of the polymerization process. Regardless of their hydrophilicity, all the swollen pOEMA microgels adsorb at the liquid interface and stabilize emulsions, whose flocculation state and mechanical stability depends on the microgel deformability. Unexpectedly, most emulsions remain stable upon heating above the VPTT of the microgels. Such feature highlights their extreme robustness, whose origin is discussed. This study opens new opportunities for the use of biocompatible Pickering emulsifiers.

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Stability of aqueous foam films and foams containing polymers: Discrepancies between different length scales

Cited by 33 publications

References 92 publications

Studying coalescence at different lengthscales: from films to droplets

Studying coalescence at different lengthscales: from films to droplets

Investigating Pore‐Opening of Hydrogel Foams at the Scale of Freestanding Thin Films

Pickering emulsions stabilized by thermoresponsive oligo(ethylene glycol)-based microgels: Effect of temperature-sensitivity on emulsion stability

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