Structure‐permeability relationships in silicone polymers

Abstract

SynopsisPermeability coefficients P for He, and C3H, in 12 different silicone polymer membranes were determined at 35.0"C and pressures up to 9 atm. Values of F for CO,, CH,, and C,H, were also determined a t 10.0 and 55.0"C. In addition, mean diffusion coefficients D and solubility coefficients S were obtained for CO,, CH,, and C3H, in 6 silicone polymers a t 10.0, 35.0, and 55.0"C. Substitution of increasingly bulkier functional groups in the side and backbone chains of silicone polymers results in a significant decrease in P for a given penetrant gas. This is due mainly to a decrease in E, whereas S decreases to a much lesser extent.Backbone substitutions appear to have a somewhat lesser effect in depressing than equivalent side-chain substitutions. The selectivity of a silicone membrane for a gas A relative to a gas €3, i.e., the permeability ratio &A)/&€%), may increase or decrease as a result of such substitutions, but only if the substituted groups are sufficiently bulky. The selectivity of the more highly permeable silicone membranes is controlled by the ratio S(A)/S(H). whereas the selectivity of the less permeable membranes depends on both the ratios D(A)/D(B) and S(A)/S(R). The permeability as well as the selectivity of one silicone membrane toward CO, were significantly enhanced by the substitution of a fluorine-containing side group that increased the solubility of CO, in that polymer.

Scanning X-ray nano-diffraction on eukaryotic cells

“…NOA 81 was cured through the PDMS stamp by exposure to UV-light for 2 min (8 W at 365 nm). The curing through the PDMS stamp leaves a thin layer of NOA 81 at the NOA 81/PDMS interface uncured [37,134,135] and therefore allows for sealing the device with a second layer of Kapton foil with no need for an additional glue or adhesive. After curing of the NOA 81, the PDMS stamp was carefully removed leaving the cured NOA 81 film on the Kapton foil (see Fig.…”

Polyurethane–poly(vinylidene fluoride) (PU–PVDF) thin film composite membranes for gas separation

“…Its low glass transition temperature (−129 • C) results in extremely high permeation through the membrane for a wide range of gases due to the flexible polymer backbone. However, it is limited in mechanical strength and selectivity particularly for highly condensable hydrocarbons in admixture with permanent gases [4][5][6]. For example, our previous work [7,8] showed that PDMS coated membrane can be plasticized by propane and propylene, resulting in significant permeance increases for both hydrocarbons and nitrogen in a quaternary mixture of propane, propylene, ethylene and nitrogen, therefore, the selectivities of hydrocarbons to nitrogen were not as high as expected.…”

“…Recently Gomes et al [18] reported the correlation of gas permselectivities with the contents of PDMS/poly(tetramethylene glycol) soft segments for the thin film membranes made from polyurethane dispersions (PUDs). It is interesting to note that n-C 4 H 10 /CH 4 selectivity for the gas mixture was higher than the ratio of individual gas permeabilities, indicating a possibility of application of this PUD material for n-C 4 H 10 /CH 4 separation.…”

“…The hard segment alternates along with soft segment, which produces distinguishing physical and mechanical properties for polyurethane. Many researchers have been investigating segmented polyurethane as a new material to improve the permselectivity for gas separation such as VOCs or CO 2 from N 2 ,H 2 S/CH 4 and O 2 /N 2 [10][11][12][13][14][15][16][17]. The structure-gas transport property correlations of those PU film membranes with a variety of singular or mixed soft segments elucidate that the gas permselectivity mainly depends on the contents and types of soft segments as well as their molecular weights.…”

Preparation, Characterization and Gas Permeation of Polyimide Mixed Matrix Membranes

“…In addition, nanoscale molecular sievesare more suitable for commercialization of nanocomposite membranes whereas they have very thin selective layers than micron-sized zeolites ormolecular sieves. Finally, the possibility of additional functionalization and surface coating of membrane that can further enhance sorption effects in these particles and raise gas selectivity, have been investigated [19][20][21]. As a new work, the functionalization of particles was performed by DMDCS.…”