Mass Transport Through PDMS/Clay Nanocomposite Membranes

Abstract

Polymer-clay composites have been produced using a broad range of polymers, such as polystyrene, polypropylene, poly(dimethylsiloxane), poly(ethylene oxide), polyamide, polycaprolactone, poly(L-lactide), liquid crystalline copolyesters, polyimide, epoxy, and poly(methylmetacrylate). The development of nanocomposites has typically involved intercalation of a suitable monomer followed by in situ polymerization. There is also a solution approach, in which the silicate clay and the polymer are intercalated in a solvent, and a melt intercalation approach, in which a molten thermoplastic is blended with silicate clay.Industrial processes such as painting, solvent degreasing, printing, dry-cleaning, polymer synthesis and fi bre spinning from solution involve the use of larger amounts of solvents such as toluene, xylene, dichloroethane, trichloroethane, dichloromethane and acetone, which contribute to the air pollution in the United States (Lahiere et al., 1993;Singh et al., 1998). Highly permeable and vapour selective polymeric membranes can be used to separate vapours from air streams and to recover such Poly(dimethylsiloxane)/clay nanocomposite membranes have been synthesized and mass transport properties through those nanocomposite membranes have been investigated. The effect of mechanical deformation on the transport properties of the PDMS (nanocomposite) membranes has also been studied. With the introduction of clay particles into the polymer matrix, mass transport is reduced, likely due to the longer diffusion path, which slows the diffusion process. The effect of membrane extension on diffusion is more complicated. Under small deformation, the permeation fl ux decreases, but under high deformation, it shows an enhanced diffusion. As the clay particle concentration increased, the effect of external deformation is reduced, and an enhanced diffusion is observed.On a synthétisé des membranes en nano-composites de polydiméthysiloxane et d'argile dans le but d'étudier leurs propriétés de transfert de matière. L'effet de la déformation mécanique sur les propriétés de transfert de ces membranes a également été étudié. Avec l'introduction des particules d'argile dans la matrice des polymères, le transfert de matière est réduit, probablement en raison du chemin de diffusion qui est plus long, ce qui ralentit le processus de diffusion. L'effet de l'extension des membranes sur la diffusion est plus compliqué. Sous faible déformation, le fl ux de perméation diminue, mais sous forte déformation, la diffusion est améliorée. Lorsque la concentration de particules d'argile augmente, l'effet de la déformation externe est réduit, et une meilleure diffusion est observée.

An integrated photonic-diffusion model for holographic sensors in polymeric matrices

“…De A and De m indicate how fast the polymer chains and complex interface react to changes. Overall, these four numbers determine how important are the polymer viscoelastic properties and the complex interface in the diffusion process, and describe whether the complex system deviates from Fickian diffusion [2,1,3].…”

“…Therefore, diffusion models coupled with rheology have been proposed for modeling these complex processes in polymeric membranes [3]. Extensions of these models account for swelling, consider microscopic (kinetic) and mesoscopic (thermodynamic) levels, energy of mixing, molecular polymer structure conformations, and interfacial interactions [1][2][3]15]. There are certainly other works that further extend these models to consider conformations and deformations [16,17], or even to molecular dynamics simulations for transport processes but in other type of systems [18].…”

“…Hybrid nanomaterials and polymer composites have been proposed to improve the physical properties of future product building blocks [1][2][3]. Understanding the phenomena of molecular interactions, together with the improved physical properties, is paramount for designing novel product components.…”

“…Molecular interactions cause the physical deformation of the polymer chains, which ultimately leads to changes in geometry and optical properties of the patterned layers of material. All these chemical and physical interactions are governed by molecular surface interactions at the nanoscale, which can be modeled mathematically [1]. In the particular case of holographic sensors, the photonic phenomena are well understood and it has been theoretically described using various modeling methodologies [4,[7][8][9][10][11][12][13][14].…”

Measuring the transient diffusion of vapor mixtures through dense membranes

“…Hasegawa et al [9] described a pervaporation unit capable of real-time analysis of a multicomponent low-pressure permeate by direct sampling in a mass spectrometer. The real-time (1× per minute) sampling of the permeate into a gas chromatograph (GC) equipped with a selective column and with a flame ionization detector was described by Liu et al [10], and this technique was applied for single-compound permeation measurements.…”