Permeation of nitrogen and water vapor through sulfonated polyetherethersulfone membrane

The novel polyetherethersulfone (PES-C) prepared from phenol-phthalein in our institute is an amorphous, rigid, tough material with good mechanical properties over a wide temperature range. To improve its water vapor permeability for the application of gas drying, the PES-C was sulfonated with concentrated sulfuric acid and transferred in sodium, cupric, and ferric salt forms. The sulfonation degree can be regulated by controlling the temperature and reaction time. Characterization of sulfonated PES-C in sodium form was made by IR. Some properties of the sulfonated PES-C, such as solubility, glass transition temperature, thermal stability, mechanical properties, and transport properties to nitrogen and water vapor have also been discussed. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2133–2140, 1997     

Sorption and diffusion of water vapor in polyimide films

Sorption and diffusion of water vapor are investigated gravimetrically for polyimide films. The activity dependence of the solubility and diffusion coefficients, S and D, respectively, is classified under four types: (1) constant S and D type, (2) dual-mode sorption and transport type, (3) dual-mode type followed by a deviation due to a plasticization effect at high vapor activity, and (4) constant S and D type followed by a deviation due to water cluster formation at high activity. For the dual-mode type, the Henry's law component is much larger than the Langmuir component except at low activity, and therefore deviation in behavior from the first type is small. S is larger for polyimides with higher content of polar groups such as carbonyl, carboxyl, and sulfonyl. D is larger for polyimides with a higher fraction of free space, with some exceptions. The polyimide from 3,3′,4,4′-biphenyltetracarboxylic dianhydride and dimethyl-3,7-diaminodibenzothiophene-5, 5-dioxide belongs to the third type and displays both large S and large D. The polyimide from 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride and 4,4′-oxydianiline belongs to the fourth type, and has the largest D but rather small S because of the hydrophobic C(CF₃)₂ groups. © 1992 John Wiley & Sons, Inc.     

Relationships between chemical structures and solubility,diffusivity, and permselectivity of 1,3-butadiene and n-butane in 6FDA-based polyimides

The solubility, diffusivity, and permselectivity of 1,3-butadiene and n-butane in seven different polyimides synthesized from 2,2-bis (3,4-carboxyphenyl) hexafluoropropane dianhydride (6FDA) were determined at 298 K. The influence of chemical structures on physical and gas permeation properties of 6FDA-based polyimides was studied. Solubility of 1,3-butadiene in 6FDA-based polyimides can be described by a dual-mode sorption model. 1,3-Butadiene-induced plasticization is considered to be associated with the increasing permeabilities of 1,3-butadiene and n-butane and the decreasing permselectivity of 1,3-butadiene vs. n-butane in the mixed gas system containing a high concentration of 1,3-butadiene. It was found that controlling the solubility of 1,3-butadiene in an unrelaxed volume in 6FDA-based polyimides is very important to maintain the high permselectivity of 1,3-butadiene vs. n-butane in the mixed gas system. Changing the  C(CF₃)₂ linkage to a  CH₂ ,  O linkage, removing methyl substituents at the ortho position of the imide linkage, and changing the p-phenylene linkage to an m-phenylene linkage in the main chains in some 6FDA-based polyimides are effective to decrease fractional free volume and restrict the solubility of 1,3-butadiene in the unrelaxed volume of a polymer matrix. The 6FDA-based polyimides restricting the solubility of 1,3-butadiene in an unrelaxed volume exhibit high separation performance in the 1,3-butadiene/n-butane mixed gas system compared with conventional glassy polymers and, therefore, are potentially useful membrane materials for the separation of 1,3-butadiene and n-butane in the petrochemical industry. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2941–2949, 1999     

Gas‐transport properties of indan‐containing polyimides

A series of indan‐containing polyimides were synthesized, and their gas‐permeation behavior was characterized. The four polyimides used in this study were synthesized from an indan‐containing diamine [5,7‐diamino‐1,1,4,6‐tetramethylindan (DAI)] with four dianhydrides [3,3′4,4′‐benzophenone tetracarboxylic dianhydride (BTDA), 3,3′4,4′‐oxydiphthalic dianhydride (ODPA), (3,3′4,4′‐biphenyl tetracarboxylic dianhydride (BPDA), and 2,2′‐bis(3,4′‐dicarboxyphenyl) hexafluoropropane dianhydride (6FDA)]. The gas‐permeability coefficients of these four polyimides changed in the following order: DAI–BTDA < DAI–ODPA < DAI–BPDA < DAI–6FDA. This was consistent with the increasing order of the fraction of free volume (FFV). Moreover, the gas‐permeability coefficients were almost doubled from DAI–ODPA to DAI–BPDA and from DAI–BPDA to DAI–6FDA, although the FFV differences between the two polyimides were very small. The gas permeability and diffusivity of these indan‐containing polyimides increased with temperature, whereas the permselectivity and diffusion selectivity decreased. The activation energies for the permeation and diffusion of O₂, N₂, CH₄, and CO₂ were estimated. In comparison with the gas‐permeation behavior of other indan‐containing polymers, for these polyimides, very good gas‐permeation performance was found, that is, high gas‐permeability coefficients and reasonably high permselectivity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2769–2779, 2004     

Sorption and transport of water vapor in alginic acid,sodium alginate,and alginate-cobalt complex films

The sorption and the transport of water vapor in films of alginic acid (G1), sodium alginate (G1Na), and alginate-cobalt complex (G1Co) were studied at 30°C by employing the weighing method. Sorption isotherms for all films of G1, G1Na, G1Co were of type II in the Brunauer's classification. The integral absorption from, and desorption to, zero pressure were non-Fickian type for all films studied. The mean permeability coefficient P , which was determined by the cup method, increased with the increase of vapor pressure, especially in the low vapor pressure region. P for G1Na was much higher than that for G1, which mainly reflects more hygroscopic nature of G1Na than that of G1. The values of P for G1Co were lower than those for G1 at lower pressures and then approached those for G1 at higher vapor pressures. Integral diffusion coefficient D evaluated as P /S, where the solubility coefficient S was evaluated from sorption isotherms, increased rapidly with increasing water concentration and then leveled off. In the concentration region studied, the magnitude of D and its dependence on concentration for H₂O-G1Na system did not differ much from those for H₂O-G1 system. D for H₂O-G1Co system was much lower than that for H₂O-G1 system. © 1994 John Wiley & Sons, Inc.     

Water‐vapor permeation in semicrystalline and molten poly(octadecyl acrylate)

The water‐vapor permeability of poly(octadecyl acrylate) (PA‐18) was measured as a function of temperature in the region traversing its melting point (50 °C). The molten‐state permeability of PA‐18 is comparable to that of shorter side‐chain methacrylate polymers. Water permeability in the semicrystalline state of PA‐18 is similar to that of polyethylene at comparable crystallinity levels. The permeation switch, or change in permeability with the traversing of the melting point, for water is discussed in the context of previous results for other penetrants in this and other side‐chain crystalline polymers. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 979–984, 2001     

Free volume and water vapor transport properties of temperature‐sensitive polyurethanes

Segmented polyurethanes (PU) with crystalline soft segments were prepared with different crystalline polyols as soft segments. Morphology and microstructure of the PUs were investigated using Differential Scanning Calorimetry (DSC), Wide‐angle X‐ray Diffraction (WAXD), and Positron Annihilation Lifetime Spectra (PALS). Water vapor transport properties of the PU membranes were measured in the temperature range of crystal melting of their soft segments. Dependence of free volume of the PUs on temperature and the relationship between the free volume and water vapor permeability of the PU membranes were investigated. The results show that the mean free volume size and fractional free volume increase more rapidly in the temperature range of crystal melting than in other temperature intervals. In the specified temperature range, water vapor permeability of the polyester based PU membranes increases significantly, caused by the steep increase in free volume, due to crystal melting of the soft segments. Water vapor permeability of the polyester based PUs exhibits approximately direct correlation with the fractional free volume within the temperature range of crystal melting. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1865–1872, 2005     

The relative contribution of adsorption to the overall sorption and transport of small molecules in amber

In 1987, Berner and Landis reported that upon vacuum grinding of 80 million year old amber, a gas mixture was released which suggested an oxygen-rich prehistoric environment. Fundamental to their argument was the assumption that amber, an organic glass formed during the fossilization of tree sap, is a perfect sealant. Their assumption was challenged by three technical comments which collectively concluded that gases diffuse readily through amber. In order to defend their key assumption that gases are perfectly trapped in amber, Berner and Landis dismissed the data obtained through gravimetric sorption experiments as only a measure of surface adsorption rather than bulk absorption in and concomitant diffusion through the amber matrix. The validity of interpreting these gravimetric experiments as a measure of bulk diffusion is demonstrated by exploring the physical basis for interpreting gravimetric sorption data. Most importantly, new experimental gravimetric sorption data are presented which demonstrate an explicit separation of adsorption from diffusion-controlled absorption and also reveal that adsorption accounts for a very small fraction of the total sorption in amber.     

聚酰亚胺、聚砜、聚醚砜及其共混改性中空纤维膜用于醇/醚气相分离的研究

甲醇／ 甲基叔丁基醚的分离是目前具有实用意义的重要研究课题之一,采用气流吹扫式操作,研究了聚酰亚胺、不同结构的聚砜中空纤维膜在不同操作条件下,对甲醇／ 甲基叔丁基醚气相混合体系的分离性能,也研究共混改性对分离膜性能的影响。结果表明,各种材料的膜具有相近的分离行为,即随着气相中甲醇含量的增加,透过通量逐渐增大而分离系数逐渐减小,聚酰亚胺膜具有适中的透过通量,但具有很高的分离系数,在甲醇浓度低于２０ ％ 时,分离系数可达数千。采用聚醚砜共混改性的聚酰亚胺膜在未明显降低透过通量的条件下,使醇／ 醚分离系数大幅度提高,有很好的应用前景。     

Relationships between the chemical structures and the solubility,diffusivity, and permselectivity of propylene and propane in 6FDA‐based polyimides

The solubility, diffusivity, and permselectivity of propylene and propane in 40 different polyimides synthesized from 2,2‐bis(3,4‐decarboxyphenyl)hexafluoropropane dianhydride (6FDA) were determined at 298 K. The influence of the chemical structures on the physical and gas permeation properties of the 6FDA‐based polyimides was studied. The solubility of propylene in an unrelaxed volume of a polymer matrix mainly contributes to the total solubility of propylene for various 6FDA‐based polyimides. The diffusivity, the permeability of propylene, and the permselectivity in the propylene/propane mixed‐gas system depend on the solubility of propylene. This is thought to be associated with the penetrant‐induced plasticization effect. 6FDA‐based polyimides, which have a high glass‐transition temperature and a large fractional free volume, exhibit a high permeability with a relatively low permselectivity. Changing the number of  CH3 substituents in the phenylene linkage and changing the connectivity in the main chain are good ways of controlling the solubility of propylene and the corresponding permselectivity in the propylene/propane mixed‐gas system. Some 6FDA‐based polyimides restrict the solubility of propylene through the introduction of a  CONH linkage between the phenylene linkage; the  Cl substituent in the phenylene linkage at the diamine moiety exhibits a high separation performance in the mixed‐gas system. The polyimides are potentially useful membrane materials for the separation of propylene and propane in the petrochemical industry. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2525–2536, 2000     

Soluble and degradable polyimides with phenyl-2-pyridyl ether structure: Synthesis and characterization

A diamine monomer o-phenylenedioxybis(5-amino-2-pyridine) was synthesized via reduction of a dinitro compound o-phenylenedioxybis(5-nitro-2-pyridine), producing a series of new polyimides from this diamine and various commercially available aromatic dianhydrides via conventional two-stage processes. The resulting polyimides are able to form tough and transparent films, with decomposition temperatures in the range of 529–551 °C, and can be dissolved in organic polar solvents. Meanwhile, these polyimides can be degraded in a hydrazine hydrate medium, a degradation mechanism proposed by analyzing the degradation products suggests that the degradable properties could be attributed to the phenyl-2-pyridyl ether structure in the polymer. In addition, the transformation of the compound structure from dinitro compound to damine monomer in the synthetic process is discussed in respect to X-ray structure.     

一种高可溶、高光学透明含氟聚酰亚胺的合成与表征

由自制芳香二胺单体9,9-双(3,5-二氟-4-胺基苯基)芴和商品化二酐单体4,4'-(六氟异丙基)双邻苯二甲酸酐经一步法高温缩聚制备了一种新型含氟聚酰亚胺.分别用FT-IR、1HNMR和19FNMR对所制聚酰亚胺结构进行了表征.结果证实其与所设计的结构完全一致,并且酰亚胺化反应完全.该含氟聚酰亚胺表现出高的溶解性:室温下在N-甲基-2-吡咯烷酮、N,N-二甲基乙酰胺、N,N-二甲基甲酰胺、氯仿、二氯甲烷、四氢呋喃等常规溶剂中的溶解度可达10wt%以上.由该聚酰亚胺溶液所制的薄膜无色透明,截断波长在315nm,400nm波长后的透光率在84%以上.此外该含氟聚酰亚胺还表现出良好的热学性能和机械性能:玻璃化转变温度在377℃,空气和氮气中10%热失重温度均在539℃以上;其薄膜的拉伸强度在70～80MPa,断裂伸长率在4%～8%,起始模量为2.6GPa.     

Water transport in a polyketone terpolymer

Water transport in a polyketone terpolymer was analyzed performing both sorption and permeation experiments. Water vapor sorption tests were conducted at four temperatures (35, 45, 55, and 65°C) and at several activities. The analysis of sorption isotherms revealed the occurrence of water clustering. A reduction of the endothermicity of mixing as the amount of sorbed water increased was observed which is consistent with significant association of penetrant molecules in the polymer. Permeation experiments performed at 35°C at upstream pressures ranging from 4 to 25 Torr showed evidence of a reduction in water diffusivity as function of sorbed water concentration which is a typical indication of penetrant aggregation. © 1995 John Wiley & Sons, Inc.     

Solubility and glass transition in the system α-D-trehalose/water

Precipitation of trehalose dihydrate in water is observed at room temperature for trehalose concentrations higher than 47.5%w/w. Direct observations of crystal melting in water and measures of the solution density determine the thermal variations of trehalose saturationS(T) (mM) in water: ln(S(T))=ln(0.1223)-(1330/T) withR ² =0.9982. The glass transition (T_g) curve measured by DSC is lower at low concentrations and higher at high concentrations than previously reported.T _g is also measured as a function of the cooling/warming rates. Analysis of specific heat changes atT _g and associated activation energy leads to identify a most stable glassy state around the second eutectic concentration.     

The transport properties of polyimide isomers containing hexafluoroisopropylidene in the diamine residue

The effect of modification of the central moiety of the dianhydride residue and isomerism on the gas transport and physical properties were compared for six polyimides containing the hexafluoroisopropylidene group in the diamine residue. Substitution of bulkier groups within the dianhydride residue resulted in disruption of chain packing and slight increases in resistance to chain motions which led to an increase in permeability with little loss in selectivity. The permeabilities and diffusivities in the meta connected polyimide isomers were considerably lower than in the para connected polyimide isomers. Similarly, the permselectivities in the meta connected isomers were consistently higher than in the para connected isomers. These lower permeabilities and higher permselectivities were a result of the more dense packing and a significant suppression of small scale motions in the meta connected isomers. The suppression of segmental mobility in the meta connected isomers was indicated by an increase in the sub Tg transition temperatures in these materials relative to the para connected isomers. The differences in transport properties for these polyimides were attributed to contributions by several factors, including: (1) total free volume (2) distribution of free volume (3) intersegmental resistance to chain motions, and (4) intrasegmental resistance to chain motions. © 1994 John Wiley & Sons, Inc.     

The polyurethane membranes with temperature sensitivity for water vapor permeation

The size and shape of free-volume holes available in membrane materials control the rate of gas diffusion and its permeability. Based on this principle, two segmented thermo-sensitive polyurethane (TSPU) membranes with functional gates, i.e. the ability to sense and respond to external thermo-stimuli, were synthesized and used for water vapor controllable permeation. Differential scanning calorimetry (DSC), positron annihilation lifetimes (PAL), water swelling and water vapor permeability (WVP) were used to evaluate how the structure of the polyurethane (PU) and the temperature influence the free-volume holes size and the water vapor permeability (WVP) of the PU membranes. DSC study reveals that TSPU with a glass transition or a crystalline transition reversible phase shows an obvious phase-separated structure and a phase transition temperature (defined as switch temperature, T_s). PAL study indicates that the free-volume holes size of TSPU is closely related to the T_s. When the temperature is higher than the T_s, the ortho-positronium (o-Ps) lifetime (τ₃) and the average radius (R) of free-volume holes of TSPU membrane increase dramatically. As a result, the WVP of TSPU membrane shows a dramatic increase. Additionally, the water swelling and the WVP of TSPU membrane are found to depend on the inner structure of the polymer, and they also give different responses to temperature variation. When the temperature is higher than the T_s, there is a significant increase of WVP from 3.80 kg/m² day to 7.63 kg/m² day for TSPU(a) and from 4.30 kg/m² day to 8.58 kg/m² day for TSPU(b), respectively. Phase transition accompanying significant changes in free-volume holes size and WVP can be used to develop “smart membranes” with functional gates and controllable gas permeation.     

O/O and H/D separation factors for liquid/vapor permeation of water through an hydrophobic membrane

Liquid/vapor permeation of water through commercial grade hydrophobic PTFE membranes at 323<P(Torr)<160, shows enhancements in logarithmic separation factors, ln[(i'/i)] = In [(χ'/χ) _downstream/ (χ'/χ) _upstream], which differ markedly for isotope separation of oxygen and hydrogen. The prime refers to the lighter isotope and χ is the mole fraction. Thus ln[(16/18)] is found to be as large as 6 times the ratio of the vapor pressure isotope effect, ln(_o = ln (P^o'/P^o), but ln[(H/D)]/ln[_o(H/D)] is only as large as 1.3. The difference in enhancement factors indicates that membrane transport mechanisms must be different for the two separations. The unusually large separation factor for ¹⁶O/¹⁸O may be of practical interest.     

基于3,5-二胺基-N（N′,N′-正二丁基甲酰胺基苯基）-苯甲酰胺的聚酰亚胺的溶解性、热稳定性和取向性能

用制得的大体积双侧基3,5-二胺基-N（N′,N′-正二丁基甲酰胺基苯基）-苯甲酰胺（DAPDM）,与3,3′-二甲基-4,4′-二氨基二苯甲烷（DMMDA）、3,3′,4,4′-二苯醚四甲酸二酐（ODPA）采用一步法共缩聚制得聚酰亚胺共聚物。采用核磁共振对该共聚物进行了表征,对其溶解性、热稳定性、预倾角进行了分析。结...     

A spectroscopic approach to assess transport properties of water vapor in PLA

The aim of this work is to describe in detail an experimental approach to quantitatively investigate water vapor transport properties in Poly (lactic acid), PLA. The approach is based on in situ time resolved Fourier Transform Infrared Spectroscopy, FTIR, in transmission mode, and provides a mean for monitoring accurately the penetrant sorption kinetics. FTIR spectra were analyzed by a deconvolution procedure, and the area of a specific peak (at 3651 cm^-1) was directly correlated to the amount of water inside the sample. The time evolution of this area was first normalized by using a peak uninfluenced by the amount of water and then interpolated to obtain the diffusivity parameter. The results were in good agreement with those obtained by more classical, and more complex microgravimetric methods.     

Sorption of water vapor on cation-substituted vermiculite

Deformations of Na, Ca, and Ba vermiculites upon sorption of water vapor have been determined by a dilatometric method. Sequential stages in the hydration of interlayer exchange cations have been identified. The experimental results have been compared with data obtained in studies using adsorptive, calorimetric, and x-ray methods.Institute of Physical Chemistry, Russian Academy of Sciences, 117915 Moscow. Institute of Colloid Chemistry and the Chemistry of Water, Academy of Sciences of the Ukraine, Kiev. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 34–39, January, 1992.