Near-surface rheology and hydrodynamic boundary condition of semi-dilute polymer solutions

Guyard, Gabriel; Vilquin, Alexandre; Sanson, Nicolas; Jouenne, Stéphane; Restagno, Frédéric; McGraw, Joshua D.

doi:10.1039/d0sm02116d

Cited by 7 publications

(9 citation statements)

References 57 publications

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“…Moreover, the solvent‐diffusion induced increase of local concentration might create a boundary layer of polymers with concentrations high enough to be considered semi‐dilute. For such a hydrodynamic situation, the no‐slip condition might not apply any more, as elaborated in recent literature 44 . But again, due to the short contact time of the solution with the membrane inside the gap, this process is likely not relevant, especially given that the observed thickening effect does not depend on the initial feed concentration.…”

Section: Discussionmentioning

confidence: 98%

“…For such a hydrodynamic situation, the no-slip condition might not apply any more, as elaborated in recent literature. 44 But again, due to the short contact time of the solution with the membrane inside the gap, this process is likely not relevant, especially given that the observed thickening effect does not depend on the initial feed concentration. If the above stated effects were substantial, the effect should be more pronounced for higher feed concentrations that are already close to the semi-dilute regime.…”

Section: Conclusion On the Most Likely Explanation Of The Observed Th...mentioning

confidence: 99%

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Numerical and experimental investigation of the unexpected thickening effect during PolyActive™ coating of TFC membranes

Brennecke,

Clodt,

Brinkmann

et al. 2024

J Adv Manuf & Process

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In this work, we used a previously described computational fluid dynamics (CFD) model of a roll‐to‐roll coating process for the fabrication of thin‐film composite membranes to predict the final coating thickness for PolyActive™, a commercially available multiblock copolymer utilized for CO2 removal membranes. We found a strong thickening effect that could not be explained by our previous model. We investigated the process experimentally. In addition, we conducted a variety of simulations with extensions of the initial CFD model. Based on our findings, we conclude that the Marangoni effect, that is, gradients of surface tension that induce secondary flow patterns in the meniscus region, is the most likely source of the observed thickening. We explain the simulation results in order to understand the physical mechanisms at play and to show how especially surface tension gradients that arise from the particular flow structure in the meniscus may explain the additional transfer of polymer solution to the membrane. Finally, we draw some conclusions on future research and give ideas on future improvements of the process. To our knowledge, Marangoni effects for the coating of PolyActive™ were not described so far in the literature, even though it is a well‐known polymer for gas separation membranes targeted at CO2 removal. Roll‐to‐roll coating is a well‐established coating method and often believed to be suitable for the scale‐up of membrane production, therefore we think that this work will help membrane researchers who are using similar coating devices to be cautious about possible complications in the process.

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Section: Discussionmentioning

confidence: 98%

Section: Conclusion On the Most Likely Explanation Of The Observed Th...mentioning

confidence: 99%

Numerical and experimental investigation of the unexpected thickening effect during PolyActive™ coating of TFC membranes

Brennecke,

Clodt,

Brinkmann

et al. 2024

J Adv Manuf & Process

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show abstract

“…We also derived a model based on Brinkman equations and we were able to find an agreement with the experimental results. In perspective, it would be interesting to look at the role of spatial wetting patterning [66][67][68][69]. We hope that this work will open the possibility of an alternative technique to the recycling of ionic liquids.…”

Section: Discussionmentioning

confidence: 99%

Thermocapillary instability of an ionic liquid-water mixture in a temperature gradient

2021

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Ionic liquids have remarkable properties and are commonly harnessed for green chemistry, lubrication and energy applications. In this paper, we study a thermo-responsive Ionic Liquid (IL) solution which has the property of phase separating above a critical temperature, an interesting feature for the recovery of the IL-rich phase. For this purpose, we generate a temperature gradient in a microfluidic cavity where the confinement strengthens wetting effects and enhances the demixing. In this experimental configuration, we report the separation patterns along the phase diagram of the binary mixture composition. Three separation dynamics regime are identified that may display complex three-dimensional flows. In spite of this complexity, we rationalize all the observed regimes. Only two regimes lead to a complete spatial separation of the two phases. Interestingly, one is reminiscent of a Marangoni instability in radial geometry, even at confinement below 100 µm. We believe this work will find applications in the recycling of ionic liquids.

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“…20 Returning to the advances in practical applications, Guyard et al recently used TIRM to study the near-interface rheology and hydrodynamic boundary condition of semidilute polymer solutions. 72 They found that the monomer charge played a key role in confined polymer dynamics. In neutral polymer solutions, a chain-sized layer of the polymer was formed at the solid-liquid interface, shifting the no-slip plane above the interface.…”

Section: Progress In Different Applicationsmentioning

confidence: 99%

Total internal reflection microscopy: a powerful tool for exploring interactions and dynamics near interfaces

Liu

Ngai

2023

Soft Matter

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Near-surface rheology and hydrodynamic boundary condition of semi-dilute polymer solutions

Abstract: Understanding confined flows of complex fluids requires simultaneous access to the mechanical behaviour of the liquid and the boundary condition at the interfaces. Here, we use evanescent wave microscopy to...

Cited by 7 publications

References 57 publications

Numerical and experimental investigation of the unexpected thickening effect during PolyActive™ coating of TFC membranes

Numerical and experimental investigation of the unexpected thickening effect during PolyActive™ coating of TFC membranes

Thermocapillary instability of an ionic liquid-water mixture in a temperature gradient

Total internal reflection microscopy: a powerful tool for exploring interactions and dynamics near interfaces

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