Gas sorption, diffusion, and permeation in poly(dimethylsiloxane)

Abstract

The permeability of poly(dimethylsiloxane) [PDMS] to H2, O2, N2, CO2, CH4, C2H6, C3H8, CF4, C2F6, and C3F8, and solubility of these penetrants were determined as a function of pressure at 35 °C. Permeability coefficients of perfluorinated penetrants (CF4, C2F6, and C3F8) are approximately an order of magnitude lower than those of their hydrocarbon analogs (CH4, C2H6, and C3H8), and the perfluorocarbon permeabilities are significantly lower than even permanent gas permeability coefficients. This result is ascribed to very low perfluorocarbon solubilities in hydrocarbon‐based PDMS coupled with low diffusion coefficients relative to those of their hydrocarbon analogs. The perfluorocarbons are sparingly soluble in PDMS and exhibit linear sorption isotherms. The Flory–Huggins interaction parameters for perfluorocarbon penetrants are substantially greater than those of their hydrocarbon analogs, indicating less favorable energetics of mixing perfluorocarbons with PDMS. Based on the sorption results and conventional lattice solution theory with a coordination number of 10, the formation of a single C3F8/PDMS segment pair requires 460 J/mol more energy than the formation of a C3H8/PDMS pair. A breakdown in the geometric mean approximation of the interaction energy between fluorocarbons and hydrocarbons was observed. These results are consistent with the solubility behavior of hydrocarbon–fluorocarbon liquid mixtures and hydrocarbon and fluorocarbon gas solubility in hydrocarbon liquids. From the permeability and sorption data, diffusion coefficients were determined as a function of penetrant concentration. Perfluorocarbon diffusion coefficients are lower than those of their hydrocarbon analogs, consistent with the larger size of the fluorocarbons. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 415–434, 2000

Selective, Room-Temperature Transformation of Methane to C1 Oxygenates by Deep UV Photolysis over Zeolites

“…O 2 permeability decreases from 10,083˘936 Barrer at 298 K to 7024˘1050 Barrer at 333 K, while O 2 diffusivity diminishes from 5.47ˆ10´8˘1.36ˆ10´8 cm 2¨s´1 at 298 K to 3.46ˆ10´8˘7.72ˆ10´9 cm 2¨s´1 at 333 K. These values are in good agreement with those reported in the literature [17,[22][23][24][25]32,33]. However, in spite of the high oxygen permeability, the ideal O 2 /N 2 selectivity of pure PTMSP is very low, ranging from 1.32˘0.12 at 298 K to 0.94˘0.41 at 333 K. This is a characteristic behavior of PTMSP due to its high free volume and the fact that the weakly and rigid molecular sieving framework is more prone to changes in solubility than diffusivity [24,32].…”

Hydrophilic surface modification of PDMS for droplet microfluidics using a simple, quick, and robust method via PVA deposition

“…Its attractiveness as a material is due to a wide and varied set of advantages that include low cost, chemical inertness, non-toxicity, and the ability to translate features in the micrometer range 3 . In addition, it is optically transparent and permeable to gases 4 . It is an elastic and physically robust material that is reversibly deformable, and it can be used to make components, including valves and pumps, in microfluidic devices 5 .…”

A Microfluidic Device for Kinetic Optimization of Protein Crystallization and In Situ Structure Determination

“…7 The present device further allows control over the rate and extent of water vapor transport through the permeable poly(dimethylsiloxane) (PDMS) membrane. 8 The extent of dehydration can be directly regulated by filling the wells overlaying each reaction site with a solution of well-defined vapor pressure and sealed with clear adhesive tape. Over the course of FID-driven crystallization, water in the well solution passes through the membrane by vapor diffusion, equilibrating with the contents of the reactor until the osmotic potentials of both solutions match.…”