Using refractive index gradients to measure diffusivity between liquids

Gaffney, C.; Chau, Cheuk-Kin

doi:10.1119/1.1328350

Cited by 32 publications

(8 citation statements)

References 9 publications

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“…2,[6][7] The diffusion of molecular species into polymer matrices is usually measured on bulky materials via gravimetry and pressure decay methods 8 or by techniques based on refractive index variations. 9 Conversely, when small polymer masses are involved, dedicated expensive and time consuming laboratory techniques such as nuclear magnetic resonance, [10][11] infrared spectroscopy, 12 and neutron reflectometry 13 are frequently needed. Some attempts to measure diffusivity in thin films via UV-Vis spectroscopy have been done using chromophore analytes, 14 but the use of these colored compounds aims to detect opportunely labelled molecules and then, it cannot be employed for uncolored species.…”

mentioning

confidence: 99%

Thin Polymer Films: Simple Optical Determination of Molecular Diffusion Coefficients

Lova

Megahd

Comoretto

2019

ACS Appl. Polym. Mater.

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The possibility to assess diffusion coefficients of small molecules in packaging polymer films directly on the shelf, or even along the fabrication line, without the use laboratory equipment commonly employed for gravimetric methods would represent a paradigm changer in the evaluation of barrier properties and byproduct formation in goods packaging and device encapsulation. In this work, we demonstrate a simple, effective and versatile method for the determination of the molecular diffusion coefficients that exploits simple UV-Vis spectroscopy and is suitable for any polymer film. This simple method also allows the direct identification of the intercalating molecule without the need for chemical targeting or of complex laboratory equipment. For this purpose, we report on the assessment of diffusion coefficients of both polar and non-polar molecules including water, ammonia, methanol, ethanol, toluene, and even hexafluorobenzene into polyvinyl chloride wrap commercialized for food packaging.

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confidence: 99%

Thin Polymer Films: Simple Optical Determination of Molecular Diffusion Coefficients

Lova

Megahd

Comoretto

2019

ACS Appl. Polym. Mater.

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“…Monitoring of the density of guest molecules in a nanoporous host material via IFM exploits the fact that the optical density n and, hence, the velocity of the light passing this material, is a function the guest concentration c. This access to the measurement of concentrations and, with their variation, of diffusivities has found widespread application for diffusion measurement with liquid mixtures (Gaffney and Chau 2001;Rashidnia and Balasubramaniam 2002;Sun and Pu 2016). Transfer of this measuring principle to diffusion in zeolites, however, proved to be quite a long way, with first attempts in already as early as 1978 at a device at the Carl-Zeiss-Parent company in Jena, temporarily made available for first attempts (Kärger et al 1978), with the establishment of a first independent device for this type of measurement in Leipzig (Schemmert et al 1999a(Schemmert et al , 1999b.…”

Section: Microimaging By Interference Microscopy (Ifm)mentioning

confidence: 99%

Application of microimaging to diffusion studies in nanoporous materials

et al. 2020

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Microimaging on the basis of, respectively, interference microscopy and IR microscopy permit the observation of the distribution of guest molecules in nanoporous solids and their variation with time. Thus attainable knowledge of both concentration gradients and diffusion fluxes provides direct access to the underlying diffusion phenomena. This includes, in particular, the measurement of transport diffusion under transient, i. e. under non-equilibrium conditions, and of self- or tracer diffusion on considering the rate of tracer exchange. Correlating the difference in guest concentration close to the external surface to its equilibrium value with the influx into the nanoporous solid, microimaging does as well allow the direct determination of surface resistances. Examples illustrating the variety of information thus attainable include the comparison of mass transfer under equilibrium and non-equilibrium conditions, single- and multicomponent diffusion and chemical reactions. They, finally, introduce into the potentials of microimaging for an in-depth study of mass transfer in mixed-matrix membranes. This tutorial review may serve as first introduction into the topic. Further references are linked for the interested reader.

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“…Diffusion coefficient of vapor molecules through polymeric films is usually determined by methods such as gravimetry [1] and pressure decay, [2] or by optical techniques like microscopy, [3] infrared spectroscopy, [4] and refractive index variations. [5] These techniques remained substantially unchanged for the last decades and currently do not allow fast and in-situ measurements. Moreover, when only a small amount of polymer is available more sophisticated approaches including NMR, and neutron reflectometry are required.…”

Section: Introductionmentioning

confidence: 99%

All-polymer Planar Photonic Crystals as an Innovative Tool for the Analysis of Air

2020

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The possibility to evaluate the molecular diffusivity in polymer thin films used for packaging and device encapsulation directly in-situ would represent a paradigm changer in the assesment of barrier properties and of air quality. Indeed, employing the packaging itself as a smart sensor could lead to waste reduction and mitigate food poisoning effects. In this work, we demonstrate a new technique that exploits simple UV-Vis reflectance spectroscopy to identify the kinetic of diffusion of small molecules in the vapor phase through polymer thin films and polymer multilayered structures. The new method allows then to assess the presence of the analyte in air and its diffusion coefficient in agreement with gravimetric data reported in literature.

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Using refractive index gradients to measure diffusivity between liquids

Cited by 32 publications

References 9 publications

Thin Polymer Films: Simple Optical Determination of Molecular Diffusion Coefficients

Thin Polymer Films: Simple Optical Determination of Molecular Diffusion Coefficients

Application of microimaging to diffusion studies in nanoporous materials

All-polymer Planar Photonic Crystals as an Innovative Tool for the Analysis of Air

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