CO2‐facilitated transport through poly(N‐vinyl‐γ‐sodium aminobutyrate‐co‐sodium acrylate)/polysulfone composite membranes

Poly(N‐vinyl‐γ‐sodium aminobutyrate‐co‐sodium acrylate) (VSA–SA)/polysulfone (PS) composite membranes were prepared for the separation of CO₂. VSA–SA contained secondary amines and carboxylate ions that could act as carriers for CO₂. At 20°C and 1.06 atm of feed pressure, a VSA–SA/PS composite membrane displayed a pure CO₂ permeation rate of 6.12 × 10^?6 cm³(STP)/cm² s cmHg and a CO₂/CH₄ ideal selectivity of 524.5. In experiments with a mixed gas of 50 vol % CO₂ and 50 vol % CH₄, at 20°C and 1.04 atm of feed pressure, the CO₂ permeation rate was 9.2 × 10^?6 cm³ (STP)/cm² s cmHg, and the selectivity of CO₂/CH₄ was 46.8. Crosslinkages with metal ions were effective for increasing the selectivity. Both the selectivity of CO₂ over CH₄ and the CO₂ permeation rate had a maximum against the carrier concentration. The high CO₂ permeation rate originated from the facilitated transport mechanism, which was confirmed by Fourier transform infrared with attenuated total reflectance techniques. The performance of the membranes prepared in this work had good stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 275–282, 2006     

Gas permeability and permselectivity of plasma‐treated polyethylene membranes

The effects of NH₃‐plasma and N₂‐plasma treatments on rubbery polyethylene (PE) membranes on the permeation behavior for carbon dioxide (CO₂), O₂, and N₂ were investigated with permeability measurements. The NH₃‐plasma and N₂‐plasma treatments on PE membranes increased both the permeation coefficient for CO₂ and the ideal separation factor for CO₂ with respect to N₂. For O₂ transport, both the permeation coefficient for O₂ and the ideal separation factor for O₂ with respect to N₂ were increased. NH₃‐plasma and N₂‐plasma treatments on polymer membranes possibly bring about an augmentation of permeability and permselectivity simultaneously. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 383–387, 2006     

Mechanism of gas transport of NH3‐plasma‐treated poly(phenylene oxide) membrane

The effect of NH₃‐plasma treatment on glassy poly(phenylene oxide) (PPO) membranes on the diffusion process for carbon dioxide (CO₂), oxygen (O₂), and nitrogen (N₂) was investigated from the permeability measurements. The sorption equilibria and permeation behavior for O₂ and CO₂ in untreated PPO membranes were simulated well in terms of the dual‐mode sorption and mobility model. For O₂ transport, NH₃‐plasma treatment on PPO membrane had an influence on the diffusion process of Henry's law species, whereas for CO₂ transport, it promoted the transport of Langmuir mode, presumably through an increased Langmuir capacity constant for CO₂. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1845–1852, 2000     

Gas permeability and permselectivity of plasma‐treated polypropylene membranes

The effects of NH₃‐plasma and N₂‐plasma treatment on rubbery polypropylene (PP) membrane upon permeation behavior for CO₂, O₂, and N₂ were investigated from their permeability measurements. The NH₃‐plasma and N₂‐plasma treatment on PP membranes could increase both the permeability coefficient for CO₂ and the ideal separation factor for CO₂ relative to N₂. For O₂ transport, both the permeability coefficient for O₂ and the ideal separation factor for O₂ relative to N₂ also increased. NH₃‐plasma and N₂‐plasma treatment on PP membranes possibly brings about an augmentation of permeability for CO₂ and permselectivity of CO₂ relative to N₂ simultaneously, but unfortunately the plasma‐treated PP membrane does not reach the level of CO₂ separation membrane. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Effect of the casting solvent on the free‐volume characteristics and gas permeability of poly[1‐(trimethylsilyl)‐1‐propyne] membranes

The effect of the casting solvent on the structure of poly[1‐(trimethylsilyl)‐1‐propyne] (PTMSP) membranes was investigated experimentally. The PTMSP membranes were cast from solutions of cyclohexane, toluene, and tetrahydrofuran; the membranes were characterized by the positron annihilation lifetime spectroscopy (PALS) technique and by gas‐permeation measurements of O₂, N₂, and CO₂. The decay curves from the positron annihilation lifetime spectroscopy gave the best fit when two long‐life components (τ₃ and τ₄, τ₃ < τ₄) were employed. This suggests that two types of free volume existed in the PTMSP membranes. The size and number density of τ₄, which was characteristic for PTMSP, decreased in the following order of the casting solvents: cyclohexane > toluene > tetrahydrofuran. The order was consistent with the order of gas permeability. A good correlation was observed between the permeability and the structural parameter that denoted the free‐volume size and the number density of τ₄. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 497–501, 2003     

Gas permeation through water‐swollen polysaccharide/poly(vinyl alcohol) membranes

The effect of Na‐alginate content on the gas permeation properties of water‐swollen membranes prepared by varying Na‐alginate and poly(vinyl alcohol) (PVA) content in membranes was investigated. The influences of water content and crystallinity of the membranes on the gas permeation performance of the water‐swollen membranes were studied. The gas permeation rate and selectivity of Na‐alginate/PVA water‐swollen membranes were compared with those of the dry membranes. The permeation rates of nitrogen and carbon dioxide through water‐swollen membranes were in the range of 0.4–7.6 × 10^?7 to 3.7–8.5 × 10^?6 cm³ (STP)/cm² s^?1 cmHg^?1, which were 10,000 times higher than those of dry‐state membranes. The permeation rates of mixture gases through water‐swollen Na‐alginate/PVA membranes were found to increase exponentially with the increase of Na‐alginate content, whereas carbon dioxide concentration in permeates was decreased linearly. It was found that the gas permeance of the water‐swollen membranes increased with increasing the Na‐alginate content in the membrane. Gas permeation rates of the water‐swollen Na‐alginate/PVA membranes increased with increasing the water content in the membrane and decreasing the crystallinity of the membrane. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3225–3232, 2004     

Effects of plasma treatment on CO2 plasticization of poly(methyl methacrylate) gas‐separation membranes

To suppress undesirable plasticization effects of condensable gas (CO₂) in high pressure gas‐separation process, a surface‐modified poly(methyl methacrylate) (PMMA) membrane prepared by a plasma treatment was synthesized in this study. The pressure dependencies of permeability were analyzed to characterize the plasticization phenomenon and how it can be controlled by the plasma modification. FTIR‐ATR and TGA results suggest that the plasma treatment leads to surface crosslinking of PMMA membrane. Thus, the plasticization effect resulting from sorbed CO₂ on the Ar‐plasma–treated PMMA membrane was significantly reduced, but the reduction in permeability was lower than that of other crosslinking modification methods. The reduction of the CO₂ permeability contributes to a major part to the selectivity of He/CO₂ for the Ar‐plasma–treated PMMA membranes. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 395–401, 2004     

Synthesis of a poly(methyl methacrylate)‐b‐poly[2‐(N,N‐dimethylamino) ethyl methacrylate] block copolymer and its effects on the surface charges and pH‐responsive properties of poly(vinylidene fluoride) blend membranes

A poly(methyl methacrylate) (PMMA)‐b‐poly[2‐(N,N‐dimethylamino) ethyl methacrylate] (PDMAEMA) block copolymer was successfully synthesized by a reversible addition–fragmentation chain‐transfer method. The resulting copolymer was used to prepare poly(vinylidene fluoride) blend membranes via a phase‐inversion technique. The polymorphism, structure, and properties of the blend membranes were investigated by Fourier transform infrared spectrometry, scanning electron microscopy (SEM), ζ potential analysis, and filtration. The results indicate that PMMA‐b‐PDMAEMA could migrate onto the surface of the membrane during the coagulation process, and more of the β‐crystal phase appeared with the increase of the block copolymer in the membranes. The surface morphology and cross section of the membranes were also affected by the copolymer, as shown by SEM. The ζ‐potential results show that the surface charges of the membrane could be changed from positive to negative at an isoelectric point as the pH increased. The blend membrane also exhibited good pH sensitivity, and its water flux showed a great dependence on pH. The filtration experiment also indicated that the blend membrane had good hydrophilicity and antifouling properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40685.     

Crosslinking and stabilization of nanoparticle filled poly(1‐trimethylsilyl‐1‐propyne) nanocomposite membranes for gas separations

Poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) has been crosslinked using 4,4′‐diazidobenzophenone bisazide to improve its chemical and physical stability over time. Crosslinking PTMSP renders it insoluble in good solvents for the uncrosslinked polymer. Gas permeability and fractional free volume decreased as crosslinker content increased, while gas sorption was unaffected by crosslinking. Therefore, the reduction in permeability upon crosslinking PTMSP was due to decrease in diffusion coefficient. Compared with the pure PTMSP membrane, the permeability of the crosslinked membrane is initially reduced for all gases tested due to the crosslinking. By adding nanoparticles (fumed silica, titanium dioxide), the permeability is again increased; permeability reductions due to crosslinking could be offset by adding nanoparticles to the membranes. Increased selectivity is documented for the gas pairs O₂/N₂, H₂/N₂, CO₂/N₂, CO₂/CH and H₂/CH₄ using crosslinking and addition of nanoparticles. Crosslinking is successful in maintaining the permeability and selectivity of PTMSP membranes and PTMSP/filler nanocomposites over time. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Surface modification of poly(ether sulfone) ultrafiltration membranes by low‐temperature plasma‐induced graft polymerization

Low‐temperature helium plasma treatment followed by grafting of N‐vinyl‐2‐pyrrolidone (NVP) onto poly(ether sulfone) (PES) ultrafiltration (UF) membranes was used to modify commercial PES membranes. Helium plasma treatment alone and post‐NVP grafting substantially increased the surface hydrophilicity compared with the unmodified virgin PES membranes. The degree of modification was adjusted by plasma treatment time and polymerization conditions (temperature, NVP concentration, and graft density). The NVP‐grafted PES surfaces were characterized by Fourier transform infrared attenuated total reflection spectroscopy and electron spectroscopy for chemical analysis. Plasma treatment roughened the membrane as measured by atomic‐force microscopy. Also, using a filtration protocol to simulate protein fouling and cleaning potential, the surface modified membranes were notably less susceptible to BSA fouling than the virgin PES membrane or a commercial low‐protein binding PES membrane. In addition, the modified membranes were easier to clean and required little caustic to recover permeation flux. The absolute and relative permeation flux values were quite similar for the plasma‐treated and NVP‐grafted membranes and notably higher than the virgin membrane. The main difference being the expected long‐term instability of the plasma treated as compared with the NVP‐grafted membranes. These results provide a foundation for using low‐temperature plasma‐induced grafting on PES with a variety of other molecules, including other hydrophilic monomers besides NVP, charged or hydrophobic molecules, binding domains, and biologically active molecules such as enzymes and ribozymes. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1699–1711, 1999     

Gas permeation properties of poly(2,5‐benzimidazole) derivative membranes

In this article, three novel polymers based on poly(2,5‐benzimidazole) (ABPBI) were synthesized by introducing propyl, isobutyl or n‐butyl groups to its side chain through an alkyl substitution reaction. FTIR and ¹³C NMR were applied to confirm the formation of corresponding chemical groups. Their physical properties including crystallinity, thermal stability, mechanical strength, and micro‐morphology were also characterized. Their solubility in common solvents were also tested to see if the modification will bring any improvement. Gas permeation properties of three derivative membranes prepared by a casting and solvent‐evaporation method were tested with pure gases including H₂, N₂, O_2, CH₄, and CO₂. It has been revealed that gas with a smaller molecular size owned a larger permeability. This means gas permeation in all prepared membranes should be diffusivity selective. Among all three modified ABPBI membranes, isobutyl substitution modified ABPBI (IBABPBI) showed the best selectivity of H₂ over other gases such as N₂ (～185) and CO₂ (～6.3) with a comparable permeability (～9.33 barrer) when tested at 35°C and 3.0 atm. Testing temperature increase facilitated gas permeation for all three membranes obviously; while in term of gas selectivity temperature increase showed diverse alteration because it brought variable impact on gas solubility of different gases. Even so, IBABPBI membrane still owned acceptable selectivity of H₂ over N₂ (～118) and CO₂ (～6.3) with an almost doubled permeability (～17.5 barrer) when tested at 75°C and 3.0 atm. Additional tests showed that running at high pressure did not bring any obvious deterioration to gas separation performance of IBABPBI membrane. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40440.     

Effects of crosslinking modification on the O2/N2 separation characteristics of poly(phenyl sulfone)/poly(bisphenol A‐co‐4‐nitrophthalic anhydride‐co‐1,3‐phenylenediamine) blend membranes

A series of blend membranes of poly(phenyl sulfone) (PPSU) with poly(bisphenol A‐co‐4‐nitrophthalic anhydride‐co‐1,3‐phenylenediamine) (PBNPI) were prepared through a solution casting method. This was done to examine the permeation characteristics of oxygen and nitrogen. The effect of the PPSU/PBNPI ratio on the membrane structure and O₂/N₂ separation performance were investigated. The results show that the permeability increased remarkably with the content of PPSU, whereas the selectivity decreased slightly. To enhance the selectivity of O₂/N₂, the blend membranes were further crosslinked with a p‐xylylenediamine agent via the immersion method. According to the Fourier transform infrared analysis, the N? H group was formed on the imide group of PBNPI. Therefore, we suggest that during the crosslinking modification, the PBNPI served as a crosslinkable polymer; this resulted in increased crosslinking efficiency with PBNPI content. The high‐resolution X‐ray diffraction and melting point method results show that crosslinking modification improved the selectivity with an acceptable loss in permeability along with increased crystallinity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Influence of γ‐irradiation on poly(methyl methacrylate)

Poly(methyl methacrylate) (PMMA) was γ‐irradiated (5–20 kGy) by a ¹³⁷Cs source at room temperature in air. The changes in the molecular structure attributed to γ‐irradiation were studied by mechanical testing (flexure and hardness), size‐exclusion chromatography, differential scanning calorimetry, thermal gravimetric analysis, and both Fourier transform infrared and solution ¹³C‐NMR spectroscopy. Scanning electron microscopy was used to investigate the influence of the dose of γ rays on the fracture behavior of PMMA. The experimental results confirm that the PMMA degradation process involves chain scission. It was also observed that PMMA presents a brittle fracture mechanism and modifications in the color, becoming yellowish. The mechanical property curves show a similar pattern when the γ‐radiation dose increases. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 886–895, 2002     

Synthesis and thermal properties of poly(methyl methacrylate)‐poly(L‐lactic acid)‐poly(methyl methacrylate) tri‐block copolymer

Poly(methyl methacrylate)‐poly(L ‐lactic acid)‐poly(methyl methacrylate) tri‐block copolymer was prepared using atom transfer radical polymerization (ATRP). The structure and properties of the copolymer were analyzed using infrared spectroscopy, gel permeation chromatography, nuclear magnetic resonance (¹H‐NMR, ¹³C‐NMR), thermogravimetry, and differential scanning calorimetry. The kinetic plot for the ATRP of methyl methacrylate using poly(L ‐lactic acid) (PLLA) as the initiator shows that the reaction time increases linearly with ln[M]₀/[M]. The results indicate that it is possible to achieve grafted chains with well‐defined molecular weights, and block copolymers with narrowed molecular weight distributions. The thermal stability of PLLA is improved by copolymerization. A new wash‐extraction method for removing copper from the ATRP has also exhibits satisfactory results. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation of thermal‐responsive poly(propylene) membranes grafted with n‐isopropylacrylamide by plasma‐induced polymerization and their water permeation

Poly(propylene) (PP) membrane grafted with poly(N‐isopropylacrylamide) (PNIPAAm), which is known to have a lower critical solution temperature (LCST) at around 32°C, was prepared by the plasma‐induced graft polymerization technique. Graft polymerization of PNIPAAm onto a PP membrane was confirmed by microscopic attenuated total reflection/Fourier transform IR spectroscopy. The grafting yield of PNIPAAm increased with the concentration of N‐isopropylacrylamide monomer and the reaction time of graft polymerization. The average pore size of the PP membrane also affected the grafting yield. From the field emission scanning electron microscopy (FE‐SEM) measurement, we observed a morphological change in the PP‐g‐PNIPAAm membrane under wet conditions at 25°C below LCST. The permeability of water through the PP‐g‐PNIPAAm membrane was controlled by temperature. The PP‐g‐PNIPAAm membrane (PN05 and PN10) exhibited higher water permeability (L_p) than the original PP substrate membrane below LCST. As the temperature increased to above LCST, L_p gradually decreased. In addition, the graft yield of PNIPAAm and the average pore size of the PP substrate influenced water permeability. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1168–1177, 2002; DOI 10.1002/app.10410     

Improvement of the water selectivity of ULTEM poly(ether imide) pervaporation films by an allylamine‐plasma‐polymerized layer

The wettability and surface energy of extruded ULTEM poly(ether imide) films strongly increased (the water contact angle varied from 75 to 38° and the surface energy varied from 45.3 to 59.5 mJ m^?2, respectively) with the deposition of an allylamine‐plasma‐polymerized layer and were characterized with X‐ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy according to the experimental parameters. Pervaporation tests for dehydrating the water/ethanol azeotropic mixture were performed at 40°C with nontreated and plasma‐treated ULTEM films for 15, 30, 60, and 120 min. No significant difference was noticed in the total flow (ca. 2.5 g/m² h) among the various films. However, for the 30‐min duration, a great increase in the water selectivity from 850 to 10,850 was measured, and it was related to the higher N/C ratio and the presence of amide groups on the surface. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2088–2096, 2005     

Gas transport properties of poly(ethylene‐2,6‐naphtalene dicarboxylate) films: Influence of crystallinity and orientation

H₂ and CO₂ transport properties were investigated on semicrystalline poly(ethylene‐2,6‐dicarboxylate naphtalene) (PEN) films and biaxially stretched films and analyzed in terms of solubility and diffusion. The decrease of the permeability observed on the thermally crystallized samples has been described by Maxwell's law. No change of the sorption properties of the amorphous phase has been noticed as a function of the thermal treatment and the evolution of the diffusion coefficient has been related to a tortuosity effect. The low permeability measured on the biaxially stretched film is related to both a change of the free volume sizes distribution and a tortuosity effect. The interesting barrier properties of the biaxially stretched film are kept even after annealing the film at 250°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1849–1857, 2003     

Gas‐transport properties through cation‐exchanged sulfonated polysulfone membranes

Sulfonated polysulfone (SPS) membranes were prepared, and the gas‐transport properties of the resulting ionic polymers were examined. Gas‐transport measurements were made on dense films of these polymers with a continuous flow technique. The sulfonation of polysulfone and the metal‐cation exchange of SPS were confirmed with Fourier transform infrared spectroscopy and electron spectroscopy for chemical analysis. The SPS membranes exchanged with the monovalent metal ions showed higher permeability coefficients than the SPS membranes exchanged with the multivalent metal ions, whereas the selectivities of all the metal‐cation‐exchanged sulfonated polysulfone (MeSPS) membranes for O₂/N₂ and CO₂/N₂ gas pairs were higher than those of SPS membranes. When the MeSPS membranes with metal cations of similar ionic radii were compared, the ideal selectivities of O₂/N₂ and CO₂/N₂ through MeSPS with divalent cations were higher than those through MeSPS with monovalent cations. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2611–2617, 2002     

Preparation and characterization of poly(methyl methacrylate)‐intercalated graphite oxide/poly(methyl methacrylate) nanocomposite

A poly(methyl methacrylate)‐intercalated graphite oxide/poly(methyl methacrylate) nanocomposite was prepared by emulsion polymerization of methyl methacrylate in the presence of graphite oxide (GO). GO was synthesized by the oxidization of natural graphite powder with KMnO₄ in concentrated sulfuric acid. The functional groups and microstructure of the oxidized graphite and the composite were carefully characterized by use of X‐ray diffraction, infrared, transmission electron microscopy, and elemental analysis. The electrical conductivity and mechanical properties were also measured. Polym. Eng. Sci. 44:2335–2339, 2004. © 2004 Society of Plastics Engineers.