三甲基硅取代PPO和三苯基硅取代PPO及其气体选择透过性能

讨论了聚２，６－二甲基－１，４－苯撑氧（ＰＰＯ）与三甲基氯硅烷和三苯基氯硅烷的反应，合成了一系列取代含量不同的三甲基硅取代ＰＰＯ（ＴＭＳ－ＰＰＯ）和三苯基硅取代ＰＰＯ（ＴＰＳ－ＰＰＯ）．研究了取代基团不同和取代含量变化对聚合物的气体选择透过性能的影响，发现ＴＭＳ－ＰＰＯ的气体透过系数随三甲基硅取代量加大而增高，分离系数下降；ＴＰＳ－ＰＰＯ的气体透过系数和分离系数都随三苯基硅取代量的增加而下降，ＴＰＳ－ＰＰＯ与ＴＭＳ－ＰＰＯ的气体溶解系数相近，扩散系数差别较大．故二者气体透过系数的不同主要是由于扩散系数的差异．从化学结构与气体透过性能关系的角度来看，若在聚合物分子中引入有较小转动自由能的大基团，则有利于气体分子的扩散透过．     

三甲基硅取代PPO和三苯基硅取代PPO及其气体选择透过性能

讨论了聚２，６－二甲基－１，４－苯撑氧（ＰＰＯ）与三甲基氯硅烷和三苯基氯硅烷的反应，合成了一系列取代含量不同的三甲基硅取代ＰＰＯ（ＴＭＳ－ＰＰＯ）和三苯基硅取代ＰＰＯ（ＴＰＳ－ＰＰＯ）。研究了取代基团不同和取代含量变化对聚合物的气体选择透过性能的影响。发现ＴＭＳ－ＰＰＯ的气体透过系数随三甲基硅取代量加大而增高，分离系数下降，ＴＰＳ－ＰＰＯ的气体透过系数和分离系数都随三苯基硅取代量的增加而下降，ＴＰ     

The effect of aryl nitration on gas sorption and permeation in polysulfone

CO_2, CH_4, O_2, and N₂ permeability and solubility of unmodified and aryl-nitrated polysulfone were determined at 35°C and pressures up to 20 atm. The degree of nitration was varied from 0 to 2 nitro groups per repeat unit. The permeability and diffusion coefficients for all gases decreased with increasing degree of nitro substitution. The decrease in gas diffusivity is attributed to a combination of decreased fractional free volume and decreased torsional mobility with increasing degree of substitution. The solubilities of N_2, O_2, and CH₄ do not show a systematic dependence on degree of substitution. However, CO₂ solubility apparently goes through a minimum as the degree of substitution is increased. CO₂ solubility may be influenced by a competition between increases in polymer polarity (favoring higher solubility) and lower free volume (favoring lower solubility) that accompanies increases in the polar nitro substituent concentration. CO₂/CH₄ solubility selectivity increases monotonically as the degree of substitution increases. CO₂/CH₄ permselectivity and diffusivity selectivity increased with increasing degree of substitution. © 1995 John Wiley & Sons, Inc.     

Effect of structure on the temperature dependence of gas transport and sorption in a series of polycarbonates

The permeabilities and solubilities of five gases are reported for bisphenol-A polycarbonate (PC), tetramethyl polycarbonate (TMPC), and tetramethyl hexafluoro polycarbonate (TMHFPC) at temperatures up to 200°C. The temperature dependence of permselectivity is discussed in terms of solubility and diffusivity selectivity changes with temperature for CO₂/CH₄ and He/N₂ gas separations. The activation energies for permeation and diffusion and the heats of sorption are also reported for each gas in the three polycarbonates. Analysis of these values provides a better fundamental understanding of the effect of polymer-penetrant interactions and polymer backbone structure on the temperature dependence of the transport and sorption properties of gases in membrane separation processes. Important factors affecting the solubility and diffusivity selectivity losses or gains with increased temperature are also identified through correlation of these data with physical properties of the gases and polymers. These conclusions provide a framework for choosing the most promising membrane materials for particular gas separations at elevated temperatures. © 1994 John Wiley & Sons, Inc.     

Polar/nonpolar gas transfer through PEO-based copolymers membranes

Two PEG-based copolymers containing two different chain extenders, as hard segments, were synthesized by 4,4′-methylenediphenyl diisocyanate (MDI). The chain extenders were 1,4-butane diol (BDO) and 1,2-ethane diamine (EDA). The application of the polyurethane (PU) and poly(urethane-urea)s (PUU)s synthesized polymers, which were characterized by Fourier transform infrared spectrometer (FTIR), differential scanning calorimetry (DSC) and atomic Force Microscopy (AFM), in the gas permeability was investigated. The obtained results indicated that by replacing the urea linkage in the polymers, the microphase separation of hard and soft segments increased. The synthesized PEG-based copolymers were semi-crystalline at room temperature. According to the DSC results, the crystallinity of the synthesized polyurethanes decreased as temperature increased. In addition, a reduction in mean surface roughness could be seen based AMF information. The gas (carbon dioxide and methane) separation properties of the polymers revealed that by replacing the urea linkage, the diffusivity, permeability and selectivity of the gases increased slightly.

The solubility and diffusivity of gases indicated he solubility domination of gas transport in these membranes. However, the sorption coefficient (S) of a particular gas was surprisingly constant for the two synthesized polymers. The CO₂ permeability increased with increasing feed pressure, while CH₄ permeability remained almost constant at both temperatures of 25°C and 35°C. The increase in temperature led to an increase in the permeability of the gases and a decrease in the gas selectivity for the both synthesized polyurethanes.     

Benzoylation of polyphenylene oxide: Characterization and gas permeability investigations

Benzoylation of polyphenylene oxide (PPO) was carried out with aromatic acid chlorides bearing specific groups at para-position (H, methyl, Br, Cl and nitro), which differ in their polarity and bulk. The reaction conditions were optimized individually to get the high degree of substitution. These materials were characterized for thermal as well as other physical properties that are known to affect the gas permeation. In a series investigated, the nitrobenzoyl substitution on PPO resulted in the highest increase in glass transition temperature and the lowest thermal stability. An estimation of the packing density parameters—fractional free volume by density measurement and the d-spacing by X-ray diffraction analysis showed an increase in the packing density. The gas permeability was found to decrease in all the cases of benzoylation. The helium and oxygen based selectivities were increased, while CO₂ based selectivities were decreased. The unusual trend observed in the gas permeation properties is explained on the basis of nature of substituent and the degree of substitution.     

Oxygen permeation in SBS-g-DMAEMA copolymer membrane prepared by UV photografting without degassing

The grafting of dimethyl amino ethyl methacrylate (DMAEMA) onto styrene–butadiene–styrene triblock copolymer membrane (SBS) was induced by UV-radiation without degassing to obtain SBS-g-DMAEMA copolymer membrane. The graft copolymer membrane was characterized by electron spectroscopy for chemical analysis (ESCA). The density and the decomposition temperature of the SBS-g-DMAEMA copolymer membrane were measured. The effects of DMAEMA grafting content and operating temperature on membrane gas permeability were investigated. It was found that the density of SBS-g-DMAEMA copolymer membrane increased with increasing DMAEMA content, whereas the decomposition temperature decreased. The changes of properties of SBS-g-DMAEMA copolymer membrane reduced the gas permeability and diffusivity of oxygen and nitrogen through the membrane, but increased the gas solubility of oxygen through the membrane and the gas selectivity between oxygen and nitrogen. When the operating temperature of gas permeation was increased, the permeability, solubility and diffusivity of oxygen and nitrogen increased but the selectivity decreased.     

Gas sorption and transport in substituted polycarbonates

The effects of molecular structure manipulation of polycarbonates on sorption and transport of various gases were studied using tetramethyl, tetrachloro, and tetrabromo substitutions onto the aromatic rings of bisphenol A polycarbonate. Solubility and permeability measurements were made at 35°C over the pressure range of 1–20 atm for a variety of gases, namely CO₂, CH₄, O₂, N₂, and He. A threefold to fourfold increase in permeability was caused by the tetramethyl substitution, whereas the tetrachloro and tetrabromo substitutions reduced the permeability relative to the tetramethyl substitution. Lower activation energies for transport were found for the tetramethyl polycarbonate relative to the unsubstituted polycarbonate. Permeability coefficients were factored into solubility and diffusion coefficients. Sorption levels increased for all substitutions, but among the substituted polymers the levels remain practically the same. Solubility data were analyzed in terms of the dual sorption model. The Henry's law solubility coefficients obtained from this analysis were found to be consistent with a predictive equation developed for rubbery polymers. The usual correlation for predicting the Langmuir sorption capacity of the model overestimates the values for the substituted polycarbonates, and a proposal for the cause of this is offered. Thermal expansion of these polymers was measured using dilatometry, and the results are used in the interpretation of the sorption data. Diffusion phenomena are explained by segmental mobility and free volume considerations. The effects of CO₂ exposure history on sorption and transport were also investigated.     

Water vapor sorption and diffusion in sulfonated aromatic polyamides

In this contribution polyamides with different sulfonation degrees were directly synthesized from a combination of sulfonated and nonsulfonated diamines and isophthaloyl chloride. They were then used as dense membranes to study water sorption and mass transport properties. The polymers were characterized by their inherent viscosity and by spectroscopic methods, and the water vapor unsteady sorption phenomena were studied using a gravimetric technique. The effect of sulfonation substitution concentration in these polymers produces very interesting and original results in a number of properties such as the ionic exchange capacity, water equilibrium sorption and diffusivity. Obtained results are discussed and explained in the light of existing theories. Sorption behavior for polymers with a low sulfonation degree, up to 30%, can be explained with Langmuir equation. With larger substitution degree (40 and 60%) an additional mechanism must be assumed to explain sorption data. Assuming the presence of two phases helps to explain the observed diffusivity results. The mass transport mechanism is assumed to be Fickian. When water activity is low diffusivity systematically decreases as the degree of sulfonation increases. However, as water activity increases less sulfonated and nonsulfonated (PA0, PA20 and PA30) behave completely different from PA40 and PA60. The first group of polymers shows a tendency to decrease the rate of diffusion as water activity increases while the second group shows the opposite behavior, with a maximum in diffusivity at intermediate water activities. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2007–2014, 2007     

Gas separation properties of aromatic poly(amide-imide) membranes

Aromatic poly(amide-imide)s were synthesized using direct 2,2-bis[N-(4-carboxyphenyl)-phthalimidyl] hexafluoropropane (6FDIA) polycondensation with various diamines containing flexible ether groups and bulky substituents. The oxygen and nitrogen gas transport in the poly(amide-imide) membranes was investigate at 35 °C with the pressure between the interval at 2-10 atm. The proposed method is expected to promote the gas permeability of the poly(amide-imide) membrane and maintain the gas selectivity. It was found that both gas permeability and selectivity of poly(amide-imide) membranes increased with increasing fractional free volume and d-spacing. The gas permeability had good correlation with the γ-transition temperature. The bulky pendent group introduced into diamine moiety of poly(amide-imide) could efficiently promote the gas permeability. For the behaviors of gas separation, the gas diffusivity coefficient and solubility selectivity controlled the gas permeability and selectivity, respectively. The sorption behavior of the aromatic poly(amide-imide) membranes can be well explained using the dual mode sorption model. The Langmuir capacity constant and Henry’s law constant increase with FFV increasing. 6F-TBAPS has the best O₂/N₂ separation performance among the poly(amide-imide) membranes.     

Gas transport properties of polyphenylene ethers

Gas transport properties of the polyphenylene ethers poly(2,6-dimethyl-1,4-phenylene oxide)PDMPO, and poly(2,6-diphenyl-1,4-phenylene oxide), PDPPO, and the thioether poly(1,4-phenylene sulfide), PPS, have been measured as a function of pressure and temperature. The PPS material and free volume correlations were used to estimate the behavior of the unavailable poly(1,4-phenylene oxide), PPO. The results show that symmetrical substitution of phenyl groups on the backbone of polyphenylene ether, PDPPO, increases the gas transport properties by one order of magnitude relative to the unsubstituted material, PPO. Symmetrical methyl substitution, PDMPO, however, increase the permeability, apparent diffusion and sorption coefficients even further. The gas transport coefficients correlate with the fractional free volume of the polymers. PDMPO has the largest fractional free volume and gas transport coefficients followed by PDPPO and the PPS. The results show that substitution of phenyl groups, which leads to polymers that have better thermal and oxidative stability than methyl substituted ones, can be a useful means for increasing free volume and gas permeability coefficients. While methyl groups appear to be more effective for the latter, the enhanced chemical stability of phenyl rings may be useful when gas separation membranes are to be used in harsh environments. © 1993 John Wiley & Sons, Inc.     

Permeation,diffusion, and sorption of dimethyl ether in fluoroelastomers

The permeation, diffusion, and sorption of dimethyl ether into a series of commercial fluoroelastomers were characterized at various pressures and temperatures. The polymers under study were based on tetrafluoroethylene and contained various amounts of other perfluorinated monomers: perfluoromethylvinylether, hexafluoropropylene, and a partially fluorinated monomer, vinylidene fluoride (VDF). These polymers were also filled with inorganic particles and cured with different techniques. The permeation rate of dimethyl ether in the elastomers examined, as well as the solubility value, increased as the content of the nonperfluorinated monomer (VDF) increased, and this was consistent with the solubility parameter theory. The diffusion coefficients, at a fixed concentration, had rather similar values for most of the elastomers examined. Both the permeability and diffusivity increased with temperature, and the corresponding activation energies were obtained for two selected polymers. The solubility of dimethyl ether, at a fixed temperature and activity, showed a linear dependence versus the weight fraction of the partially fluorinated monomer (VDF) in the polymeric matrix. The effect of the filler on the sorption and transport properties was also considered: the addition of the filler lowered the permeability and diffusivity, whereas the solubility was generally increased with respect to the crosslinked rubber. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1987–2006, 2004     

N-substitution of polybenzimidazoles: Synthesis and evaluation of physical properties

Series of N-substituted polybenzimidazoles (PBI) were synthesized using selective alkyl groups with varying bulk and flexibility, viz., methyl, n-butyl, methylene trimethylsilane and 4-tert-butylbenzyl. PBI-I based on 3,3′-diaminobenzidine (DAB) and isophthalic acid and PBI-BuI based on DAB and 5-tert-butyl isophthalic acid were chosen for N-substitution. Structural characterizations of substituted polymers by FT-IR and ¹H NMR revealed elimination of hydrogen bonding. Evaluation of their physical properties revealed that N-substitution rendered better solvent solubility in common organic solvents, more open polymer matrix, but reduced thermal properties in comparison to their respective parent PBI. 4-tert-butylbenzyl, methylene trimethylsilane or n-butyl group substituted polymers were soluble even in chlorinated solvents (CHCl₃ and TCE). Substantial variations in gas permeability of inert gases, He and Ar and attractive P_He/P_Ar selectivity, especially after methyl group substitution depicted potential of these materials for gas separation.     

以硝基、氨基修饰改性聚苯醚

将聚苯醚硝化、还原,分别合成了硝化聚苯醚和胺化聚苯醚,最高硝基、氨基取代度分别为95%、65%.讨论了各种反应条件对取代度的影响,并对修饰改性的聚苯醚进行了表征。     

Influence of side chains assembly on the structure and transport properties of comb-like polysiloxanes in hydrocarbon separation

We have synthesized a number of comb-like polysiloxanes with linear, branched, cyclic and silicon-containing substituents; most of them are new and previously not studied polymers. The physicochemical properties of comb-like polysiloxanes have been systematically investigated. Differential-scanning calorimetry and wide-angle X-ray scattering data revealed the side-chain microphase assembly for polymers with linear aliphatic substituents, while the polymers with bulky substituents did not form a microphase. It is shown that the ratio of microphase in the polymer is greater, the closer the values of the thickness of the microphase layer and the length of the cross-link. The effect of the side-chain substituent on the hydrocarbon transport properties of comb-like polysiloxanes was studied. All synthesized polymers are promising as membrane materials for a vital process of hydrocarbon separation. This is associated with an increase in the solubility selectivity of n-butane/methane because the solubility coefficient of methane sharply decreases when long side chains are introduced into the polysiloxane. It was shown for the first time that microphase forming polymers have a significantly higher butane/methane selectivity (23.2–27.5) than polysiloxanes not forming a microphase (selectivity 12.3–20.0). The effect is demonstrated on polysiloxanes with various types of side substituents. It was revealed that for the comb-like polysiloxanes, the diffusivity selectivity and permselectivity are proportional to the fraction of the side-chain microphase in the polymer. With the increase in the hydrocarbon microphase share, the diffusion coefficient of the permanent gas methane is decreasing more rapidly than n-butane, which dissolves well in hydrocarbons and plasticizes polymer. Consequently, the polymers forming the microphase have a higher selectivity C₃₊/CH₄ in the separation of a multicomponent hydrocarbons mixture.     

Selective olefin permeation through Ag(I) contained silicone rubber-graft-poly(acrylic acid) membranes

The silicone rubber (SR) based graft copolymer, SR-graft-poly(acrylic acid) (SR-g-AA), was modified by incorporating silver ion (SR-g-AA-Ag⁺) for C₄ olefin/paraffin gases separation. Olefin could be transported across the complex membrane by the silver ion facilitated transport. The permeation properties, as measured by gas chromatography equipped with a gas permeability analyzer, implied a facilitating effect for olefin. Typical trans-2-butene/n-butane selectivity in the 95.6% grafted complex membrane at 25°C is 4.0. Also, the influences of AA% grafting, measuring temperature and pressure to the permeation properties of C₄ gases were studied. In addition, the sorption behaviors of C₄ gases in SR based membranes are presented and discussed by the Flory-Huggins equation. Finally, the selectivity of solubility and diffusivity in these SR based membranes are also discussed.     

GAS SORPTION AND TRANSPORT IN POLY (PHENYLENE OXIDE)(PPO)AND ARYL-BROMINATED PPO MEMBRANES

The apparent solubility (S), concentration-average diffusivity (D), and permeability (P), for C0_2, CH_4 and N_2 through PPO and aryl-brominated PPO at 35℃for pressure ranging from 1 to 26 atm are reported. It is found that P, D, and S of the membranes to all the three gases vary with the extent of bromination. S increases with the increase of the percent of bromine in each case, but D to CO_2 increases remarkably only at higher degree of brominafion, and therefore, P to CO_2 is increased by more than 100% over a wide range ofpressure in the case. The solubility data are well described by the dual mode sorption model. It is found that the gas molecules sorbed by the Langmuir mode are relatively more immobilized and the contribution of the nonequilibrinm character of the polymer to gas permeation increases obviously for CO_2 and is hardly changed for CH_4 with increasing bromine content. These observations are interpreted in terms of changes in specific free volume (SFV)and the cohesive energy density (CED) of the polymers.     

Evaluation of substituted polycarbonates and a blend with polystyrene as gas separation membranes

The balance between the rate and the selectivity of transport of various gas pairs in a series of polycarbonates has been examined. Replacement of the four available hydrogens on the aromatic rings of the bisphenol-A unit with CH₃, Cl, or Br groups gives materials with a better balance of these two characteristics than the unsubstituted polycarbonate (PC). For example, using CH₃ substitution increases the permeability to O₂ by nearly a factor of four with no loss in O₂/N₂ selectivity compared with PC, while using Br substitution increases O₂/N₂ selectivity by 50% without any loss in O₂ permeability compared with PC. While these substitutions affect the permeability through both its mobility and solubility components, the remarkable selectivity effects are caused primarily by changes in relative mobility since the changes in solubility characteristics are nearly the same for all gases. These substitutions alter chain motions, cohesion, and packing as discussed. The tetramethylbisphenol-A polycarbonate forms miscible blends with polystyrene. These blends show absolute permeability coefficients which are lower than additivity while the selectivity of transport is greater. These effects are a result of the interactions between the two polymers.     

Imidazole-containing chitosan derivative: a new synthetic approach and sorption properties

A novel method for the synthesis of a hetaryl-containing chelate amino polymer, namely, N-(4(5)-imidazolylmethyl)chitosan (IMC), with a degree of substitution up to 0.3 was proposed. The “synthesis in gel” approach involves direct substitution of the hydroxyl group in 4(5)-imidazolylmethanol. The structures of these polymers were confirmed by ¹H NMR data. For sorption studies, IMC samples were crosslinked with epichlorohydrin and diglycidyl ethers of ethylene glycol and diethylene glycol. The degrees of swelling and sorption properties of the polymers largely depend on the crosslinking agent and the degree of crosslinking. The sorption capacities of IMC for Au^III, Pt^IV, and Pd^II ions are higher than those of the nonmodified polymer. The extraction of noble metal ions from chloride solutions becomes more selective with increasing degree of crosslinking. The sorption capacity of IMC for Co^II and Ni^II ions is higher than those of chitosan and its known N-heterocyclic derivatives.     

Preparation and application of dense poly(phenylene oxide) membranes in pervaporation

Dense flat-sheet membranes were prepared from poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) using the casting solvents chloroform and 1,1,2-trichloroethylene. X-ray diffraction, tapping mode atomic force microscopy (TM-AFM), and contact angle studies were used to characterize the membranes. The surface energy and the solubility parameters of the PPO membranes were determined from the measured contact angles and compared with the predicted ones from the group contribution method. Swelling experiments and pervaporation separation of methanol from its mixture with ethylene glycol over the entire range of concentration, 0-100%, were conducted using these membranes. Flory-Huggins theory was used to predict the sorption selectivity. The results are discussed in terms of the solubility parameter approach and as function of the morphological characteristics of the membranes. It was found that PPO membranes prepared with chloroform exhibited better pervaporation performance than PPO membranes prepared with 1,1,2-trichloroethylene.