F. Hamad

Sulfonated polyphenylene oxide–polyethersulfone thin-film composite membranes: Effect of counterions on the gas transport properties

Abstract Thin film composite membranes based on sulfonated poly(phenylene oxide) (SPPO) as the top selective layer and PES ultrafiltration membrane as the support layer, were prepared. The effect of the support membrane pore size distribution, and the effect of exchanging the proton of the sulfonic acid groups with mono-, di- and trivalent cations on the gas transport properties of the TFC membranes were studied. It was found that the resistance to gas permeation imposed by the PES support layer increased significantly upon exposure to the solvent in the coating solution. The differences in the performance of the TFC membranes having different metal cation replacing the proton of the sulfonic acid groups were explained in terms of the metal cations’ electronegativities and sizes. Very high selectivity associated with reasonable permeance was obtained when the SPPO was in the Al 3+ -form.

Study of the surface of the water treated cellulose acetate membrane by atomic force microscopy

Water treated cellulose acetate (CA) membranes surface was studied by atomic force microscopy (AFM). It was observed that when CA membrane (water untouched) was treated with water, the morphology of the surface change was detected by AFM. The roughness parameter of the surface was increased. No significant change was observed on the surface on drying the water treated membrane at room temperature for four days. The results were discussed on the basis that CA membrane contains continuous channels (network pores), which were formed in water-swollen polymer matrix. These water channels are responsible for the rejection of salt in reverse osmosis (RO) phenomenon.

Characterization of gas separation membranes prepared from brominated poly (phenylene oxide) by infrared spectroscopy

Abstract IR spectra of brominated high molecular weight PPO membranes revealed that brominating PPO at the phenyl ring results in decreasing both the COC torsional motion, and the plane CH bending, which are assigned respectively to the 1300 cm−1 and 1180 cm−1 bands in PPO. Splitting in the 1180 cm−1 band was observed at 37.4% bromination and higher, indicating different modes for CH bending that occurred as part of the methyl groups was hindered by adjacent bromine substituents. The permeability of gases in the brominated PPO membranes increased slightly in comparison to that of PPO as the degree of bromination was increased to 37.4%, however, the permeability of gases almost doubled at 60% bromination degree. The trend in the gas permeability data and the IR spectra obtained in this study both conform with and support the mechanism proposed in the literature that higher degrees of bromination are needed to enhance the permeability of gases through stiffening the PPO backbone, which increases the rate of diffusional jumps.

Effect of metal cations on the gas separation performance of sulfonated poly (phenylene oxide) membranes

The polymer polarity and density of sulfonated poly (phenylene oxide) (SPPO) membranes were manipulated by exchanging the proton of the sulfonic groups with mono-, di-, and tri-valent metal cations. The performance of the TFC membranes coated with ion-exchanged SPPO, toward the separation of CO2/CH4 and O2/N2 gas systems, showed to correlate with the location of the metal in the universal periodic table of the chemical elements. Altering the metal cation that replaces the proton of the sulfonic groups has altered: the cross-linking forces, the hindrance effects due to the voluminous metal size, and the SO3-Metal groups polarity due to the change in the metal electronegativity.

ESR spectra of spin probe in PPO membrane

Poly(phenylene oxide) (PPO) polymer’s membranes (dense) were prepared by blending spin probes (TEMPO, 5-, 12- and 16-doxylstearic aid) in the casting solution used for the preparation of membranes. It was noticed that the shape and size of the probe influence the ESR spectra of the NO z radical in the poly(phenylene oxide)membrane. Unexpectedly, from the shape of the ESR signal it was noticed that of the NO z radical of TEMPO in PPO membrane was more mobile than in water media. However, the motion of the NO z radical of 16-doxylstearic acid was higher than NO z of 5- and 12-doxylstearic acid when the radicals were in the PPO membrane. This could be due to the inductive effect from COOH group. The Hamiltonian parameters of the ESR signal indicated that all the probes were not randomly distributed in PPO membrane, but some probes were in orderly fashion. q 2002 Elsevier Science Ltd. All rights reserved.

Interaction of gaseous hydrocarbons with poly(phenylene oxide) membranes by infrared spectroscopic technique

Abstract In presence of gaseous hydrocarbons (methane, acetylene, ethane and ethylene), the infrared (IR) spectrum of poly(phenylene oxide) PPO membrane has changed at particular bands. When air or helium gas is passed through the PPO membrane sample treated by gaseous hydrocarbons, the IR spectra regained its original shape and intensity. Thus, this phenomenon is reversible and suggests the formation of an unstable complex by the physical interaction between PPO molecules and physically adsorbed gaseous hydrocarbons. Methane and acetylene reacted or affected the PPO IR spectra in the same position, while ethylene in a different position. Ethane’s effect on IR spectra of PPO was similar to that observed for ethylene. It was further observed that the physical interaction between the gaseous hydrocarbons and PPO molecules possesses kinetic characteristics, i.e. depends on time and gas partial pressure. The molecular weight of PPO and the solvent (used in casting solution) boiling point affect the extent of interaction of these gases with polymeric membranes. A plausible kinetic model has been presented.