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Donald R Paul - One of the best experts on this subject based on the ideXlab platform.
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physical aging and carbon dioxide plasticization of thin polyimide films in mixed Gas Permeation
2014Co-Authors: Jianzhong Xia, Donald R Paul, Taishung ChungAbstract:Abstract The Gas Permeation properties from thick (bulk) films have long been used as a guide to the performance of asymmetric membranes with a very thin selective skin (~100 nm). However, recent research has shown that thin films of glassy polymer with a similar thickness undergo more rapid physical aging than such thick films, leading to different Permeation characteristics. Our prior work has dealt with pure Gases, and most recently, pure CO 2 has been used to explore the difference in plasticization behavior for thick and thin films. This paper is the first effort to look at mixed Gases involving CO 2 and how thin films differ from thick films. Thick and thin films made of Matrimid, an important polymide for commercial Gas separation membranes, have been investigated by monitoring their Gas permeability and selectivity simultaneously for CO 2 /CH 4 and CO 2 /N 2 Gas mixtures. The effects of film thickness, aging time, pressure, Gas pair and Gas composition on mixed Gas behavior have been discussed in detail. The pressure dependence of pure Gas permeability has also been measured as a control. Matrimid films become more vulnerable to CO 2 plasticization as the thickness is reduced to the range of thin selective skins of asymmetric membranes and with increasing aging time. Competitive sorption/Permeation effects appear to be more pronounced and the combined effect of CO 2 plasticization and competitive sorption/Permeation on thin Matrimid films seems to be more severe for CO 2 /CH 4 feed mixtures than for CO 2 /N 2 mixtures.
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synthesis and characterization of thermally rearranged tr polymers effect of glass transition temperature of aromatic poly hydroxyimide precursors on tr process and Gas Permeation properties
2013Co-Authors: Ruila Guo, Donald R Paul, David F Sanders, Zachary P Smith, Enny D Freema, James E McgrathAbstract:Soluble aromatic polyimides containing ortho-positioned hydroxy groups were synthesized as precursors for thermal rearrangement (TR) to polybenzoxazoles (PBOs). Fully imidized polyimides with high-molecular-weights were afforded via a ‘one-pot’ solution imidization technique (i.e., ester-acid method). The poly(hydroxyimide)s were designed to vary in their glass transition temperatures (Tg) by carefully selecting dianhydride–bisaminophenol combinations to introduce various levels of chain rigidity. TR conversion (imide-to-benzoxazole conversion) occurred in solid-state films only under inert atmosphere and over a temperature range of 300–450 °C, depending on the chemical structure (chain rigidity) of precursors. The effect of the precursor Tg on TR conversion was studied using TGA, DSC, FTIR and gel fraction measurements. The TR conversion temperature of imide-to-benzoxazole rearrangement strongly depended on the precursor Tg. Thus, for example, the feasible TR temperature was successfully reduced by ∼100 °C by lowering the precursor Tg by using a bisphenol A type dianhydride in the polymer synthesis. Gas Permeation properties of representative TR systems are also reported. The TR process significantly increased Gas permeabilities while maintaining good selectivities. By correlating the TR conversion degree with Gas transport properties, there appears to be an optimal TR conversion degree that can maximize both Gas permeability and selectivity. Systematic studies on TR polymers derived from low Tg precursors were suggested to further explore this correlation.
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surface modification of polyimide membranes by diethylenetriamine deta vapor for h2 purification and moisture effect on Gas Permeation
2013Co-Authors: Huan Wang, Donald R Paul, Taishung ChungAbstract:Abstract We have demonstrated the use of diethylenetriamine (DETA) for vapor-phase modification of 6FDA-polyimide membranes for improving H 2 /CO 2 separation performance. The effectiveness of DETA as the crosslinker was compared using the conventional solution-phase and the new vapor-phase modification approaches. It is demonstrated that the latter approach is favored in view of the better membrane tensile properties, Gas Permeation properties and environmental friendliness. The effects of vapor-phase modification parameters, temperature and duration, on the effectiveness of H 2 /CO 2 separation were investigated by evaluating the Gas Permeation properties in the resultant films using pure Gas, dry-state and wet-state mixed Gases. A series resistance model for a simplified reaction progression was applied to evaluate the intrinsic Gas Permeation properties of the modified layers attained from thick films. Much thinner films, however, provide an improved means of assessment. Compared to pure Gas permeability, the H 2 permeability decreases significantly while the CO 2 permeability is almost not affected in dry-state mixed Gas tests (H 2 :CO 2 =50:50 vol%). In the wet-state mixed Gas tests (relative humidity∼50%), the H 2 permeability further drops in the modified films; the CO 2 permeability drops in the unmodified films or films with a shorter modification duration (3 min), owing to sorption competition with highly condensable water; whereas, the CO 2 permeability increases unexpectedly in membranes with extended modifications (>6 min), which is attributed to the water enhanced amine-induced sorption effect on transport when the modified membrane contains a large amount of amine groups. Overall, the DETA induced polyimide surface modification shows significant improvement for H 2 /CO 2 separation but the performance decreases when a humid feed Gas stream is used.
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Gas Permeation in poly ether imide nanocomposite membranes based on surface treated silica part 1 without chemical coupling to matrix
2006Co-Authors: S Takahashi, Donald R PaulAbstract:Abstract Nanocomposite membranes based on nano-sized SiO2 particles with chemical coupling to the polymer matrix are described with special emphasis on Gas Permeation properties. In this paper, poly(ether imide) with reactive imide rings in the backbone was used as the matrix to which the SiO2 particles were chemically bonded via an amine-containing silane coupling agent. Four types of nanocomposite membranes were prepared by solution casting and melt processing and characterized in terms of morphology and void volume formed due to adding SiO2 particles. The relative Gas permeability of the nanocomposite with chemical coupling to matrix was decreased by the presence of SiO2 particles. Diffusion coefficients computed from time lag data also decreased with SiO2 content. However, solubility coefficients computed by dividing the experimental permeability by the diffusivity obtained from the observed time lag increased with SiO2 content contrary to simple composite theory. These Permeation properties are discussed in terms of the void volume fraction estimated by density observations. In addition, TEM and SEM were used to explore the morphology of these nanocomposite membranes.
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Gas Permeation in poly ether imide nanocomposite membranes based on surface treated silica part 1 without chemical coupling to matrix
2006Co-Authors: S Takahashi, Donald R PaulAbstract:Abstract The long range objective of this research is to understand to what extent the presence of nanosized particles may change the local properties, and specifically permselectivity characteristics, of a glassy polymer matrix or whether conventional composite theory can be applied to such composites, i.e., the matrix properties are not changed by the filler. In this work, nanocomposite membranes based on an amorphous, glassy poly(ether imide) were formed by incorporating three kinds of hydrophobically treated fumed silica by solution casting and melt processing techniques. However, there is considerable evidence that these nanocomposites contain voids or defects, probably at the polymer–particle interface or within aggregates, that increase Gas permeability and decrease selectivity. Thus, the primary focus of this paper is the relation between the extent of voids formed in the nanocomposite and the Permeation properties. In addition, this paper deals with techniques for dispersing nanosized particles, fumed silica, in the polymer matrix, characterization of morphology of this mixture using TEM and SEM, and evaluation of local properties based on Gas Permeation.
Yuri Yampolskii - One of the best experts on this subject based on the ideXlab platform.
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synthesis and Gas Permeation properties of novel spirobisindane based polyimides of intrinsic microporosity
2013Co-Authors: Yulia Rogan, Ludmila Starannikova, Yuri Yampolskii, V Ryzhikh, Paola Bernardo, Fabio Bazzarelli, J C Jansen, Neil B MckeownAbstract:Three novel polyimides (PIM-PIs) with characteristics similar to a polymer of intrinsic microporosity (PIM) were prepared by the reactions of a novel spirobisindane-based dianhydride with appropriate aromatic diamines. A polymerisation procedure via in situ ester precursor formation provided PIM-PIs with very high molar masses. The Gas Permeation parameters (permeability (P), diffusion (D) and solubility (S) coefficients) were determined for these polymers. These PIM-PIs exhibit both high apparent surface areas and high Gas permeability coefficients, greater than those of most polyimides studied so far and only slightly smaller than the permeability coefficients of the archetypal polymer of intrinsic microporosity, PIM-1. Treatment of the films with alcohols results in significant increases the P values, just as has been noted for PIM-1. This enhancement is caused by an increase of the diffusion coefficients, while the solubility coefficients are much less sensitive to this treatment. However, PIM-PIs are distinguished by extremely high Gas solubility coefficients a property, which is characteristic to all PIMs.
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Gas Permeation parameters of mixed matrix membranes based on the polymer of intrinsic microporosity pim 1 and the zeolitic imidazolate framework zif 8
2013Co-Authors: Alexandra F Bushell, Peter M Budd, Ludmila Starannikova, Yuri Yampolskii, Paola Bernardo, Fabio Bazzarelli, Martin P Attfield, Christopher R Mason, Alexander Rebrov, J C JansenAbstract:Abstract Mixed matrix membranes (MMMs) based on the polymer of intrinsic microporosity PIM-1 and the zeolitic imidazolate framework ZIF-8 were prepared and their Permeation and sorption properties investigated. Self-supported films with ZIF-8 contents up to 43 vol% were studied using GC Gas Permeation apparatus and a McBain sorption microbalance. Permeability coefficients were determined for the following set of Gases: He, H 2 , O 2 , N 2 , CO 2 , CH 4 . For “as-cast” films, an increase in ZIF-8 loading results in increases in the permeability and diffusion coefficients as well as in the separation factors α (H 2 /N 2 ), α (H 2 /CH 4 ), α (He/N 2 ), α (O 2 /N 2 ) and α (CO 2 /CH 4 ). For all ZIF-8 contents studied, permeability is enhanced by treatment with ethanol. Data points on several Robeson diagrams are located above the 2008 upper bound. Free volume in MMMs containing ZIF-8 was studied using positron annihilation lifetime spectroscopy (PALS) and radio thermoluminescence (RTL) methods. It was shown that the introduction of ZIF-8 nanoparticles into the PIM-1 matrix results in an increase in free volume which may be assumed to arise from a combination of the contributions cavities and of more loosely packed polymer chains at the boundary between ZIF-8 particles and the PIM-1 matrix. The results obtained for the PIM-1/ZIF-8 MMMs are compared with literature data for other MMMs.
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new high permeable addition poly tricyclononenes with si ch3 3 side groups synthesis Gas Permeation parameters and free volume
2010Co-Authors: M L Gringolts, Yuri Yampolskii, M V Bermeshev, L E Starannikova, V P Shantarovich, E FinkelshteinAbstract:Addition polymerization of two tricyclononene monomers bearing one and two Si(CH3)3 groups was performed in the presence of Pd-containing catalysts. The polymers were obtained with high yields and were completely saturated. Good mechanical and film forming properties are observed for the polymers prepared in the presence of Pd(OAc)2/B(C6F5)3 catalyst. Their glass transition temperature was not observed until the onset of thermal decomposition (>370 °C) and the molecular weights are high (Mw up to 7 × 105). Study of Gas Permeation parameters of the obtained poly[3-(trimethylsilyl)tricyclononene-7] and poly[3,4- bis(trimethylsilyl)tricyclononene-7] showed that both glassy polymers revealed substantially high Gas permeability. Other transport characteristics (increase in permeability in the series C1−C4 alkanes and negative activation energies of Permeation) indicate that these polymers reveal so-called solubility controlled Permeation, which is typical for some extra-high permeability polymers. Positron ann...
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synthesis characterization and Gas Permeation properties of a novel group of polymers with intrinsic microporosity pim polyimides
2009Co-Authors: Bader Ghanem, Neil B Mckeown, Peter M Budd, Nasser M Alharbi, Detlev Fritsch, Kathleen Heinrich, Ludmila Starannikova, Andrei Tokarev, Yuri YampolskiiAbstract:A range of polyimides with characteristics similar to a polymer of intrinsic microporosity (PIM) were prepared by reaction with various aromatic diamines of a bis(carboxylic anhydride) incorporating a spiro-center. The polymers exhibited high surface area, as determined by nitrogen adsorption, and high thermal stability. Membrane Gas Permeation experiments showed PIM-polyimides to be among the most permeable of all polyimides and to have selectivities close to the upper bound for several important Gas pairs. A group contribution method was used to predict permeability coefficients and separation factors for further PIM-polyimide structures, revealing worthwhile targets for future synthetic efforts.
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Gas Permeation parameters and other physicochemical properties of a polymer of intrinsic microporosity polybenzodioxane pim 1
2008Co-Authors: Peter M Budd, Bader Ghanem, Neil B Mckeown, Detlev Fritsch, Ludmila Starannikova, Yuri Yampolskii, Kadhum J Msayib, N A Belov, Olga Sanfirova, V P ShantarovichAbstract:Abstract A detailed study of Gas Permeation, thermodynamic properties and free volume was performed for a novel polymer of intrinsic microporosity (PIM-1). Gas permeability was measured using both Gas chromatographic and barometric methods. Sorption of vapors was studied by means of inverse Gas chromatography (IGC). In addition, positron annihilation lifetime spectroscopy (PALS) was employed for investigation of free volume in this polymer. An unusual property of PIM-1 is a very strong sensitivity of Gas permeability and free volume to the film casting protocol. Contact with water in the process of film preparation resulted in relatively low Gas permeability ( P (O 2 ) = 120 Barrer), while soaking with methanol led to a strong increase in Gas permeability ( P (O 2 ) = 1600 Barrer) with virtually no evidence of fast aging (decrease in permeability) that is typical for highly permeable polymers. For various Gas pairs (O 2 /N 2 , CO 2 /CH 4 , CO 2 /N 2 ) the data points on the Robeson diagrams are located above the upper bound lines. Hence, a very attractive combination of permeability and selectivity is observed. IGC indicated that this polymer is distinguished by the largest solubility coefficients among all the polymers so far studied. Free volume of PIM-1 includes relatively large microcavities ( R = 5 A), and the results of the PALS and IGC methods are in reasonable agreement.
Young Moo Lee - One of the best experts on this subject based on the ideXlab platform.
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Gas Permeation properties of hydroxyl group containing polyimide membranes
2008Co-Authors: Chul Ho Jung, Young Moo LeeAbstract:A series of hydroxyl-group containing polyimides (HPIs) were prepared in order to investigate the structure-Gas Permeation property relationship. Each polymer membrane had structural characteristics that varied according to the dianhydride monomers. The imidization processes were monitored using spectroscopic and thermog-ravimetric analyses. The single Gas permeability of He, H2, CO2, O2, N2 and CH4 were measured and compared in order to determine the effect of the polymer structure and functional -OH groups on the Gas transport properties. Surprisingly, the ideal selectivity of CO2/CH4 and H2/CH4 increased with increasing level of -OH incorporation, which affected the diffusion of H2 or the solubility of CO2 in HPIs. For H2/CH4 separation, the difference in the diffusion coefficients of H2 and CH4 was the main factor for improving the performance without showing any changes in the solubility coefficients. However, the solubility coefficient of CO2 in the HPIs increased at least four fold compared with the conventional polyimide membranes depending on the polymer structures. Based on these results, the polymer membranes modified with-OH groups in the polymer backbone showed favorable Gas Permeation and separation performance.
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relationship between chemical structure of aromatic polyimides and Gas Permeation properties of their carbon molecular sieve membranes
2004Co-Authors: Ho Bum Park, Youn Kook Kim, Ji Min Lee, Sun Yong Lee, Young Moo LeeAbstract:Abstract A series of aromatic polyimides was prepared via two-step polymerization and subsequent thermal imidization to manufacture carbon molecular sieve (CMS) membranes. In order to know the effect of microstructural changes of the polyimides on the Gas Permeation properties of their CMS membranes, three copolyimides were designed and synthesized using a dianhydride and diamines with a different number of methyl substituent groups. The density, fractional free volume (FFV), and glassy transition temperature ( T g ) of the polyimides were characterized to investigate the microstructural changes of the polyimides which led to the difference in Gas Permeation properties as well as that in their physical properties. The introduction of methyl substituent group in the rigid polyimide backbone increased FFV of polyimides, and the Gas permeabilities increased typically with FFV. After an inert pyrolysis of these polyimides, similar Gas Permeation behaviors were also observed in their CMS membranes pyrolyzed at 600 and 800 °C, respectively. That is, the Gas Permeation characteristics of the polyimide due to the structural change were well kept even after pyrolysis within the temperature range used in this work. In all cases, the Gas permeabilities increased in the order He>CO 2 >O 2 >N 2 , indicating that the Gas permeabilities are in agreement with the order of the kinetic Gas diameters. The CMS membranes prepared in this study exhibited good separation properties on He/N 2 , O 2 /N 2 , and CO 2 /N 2 with satisfactory Gas permeabilities. Thereby, the present work will provide an insight into the molecular design of the polymeric precursors for the effective preparation of the CMS membranes.
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Gas Permeation properties of poly amide 6 b ethylene oxide silica hybrid membranes
2001Co-Authors: Jaehoon Kim, Young Moo LeeAbstract:Abstract The organic–inorganic hybrids of poly(amide-6-b-ethylene oxide) (PEBAX ® ) and silica were prepared via in situ polymerization of tetraethoxysilane (TEOS) using the sol–gel process and their Gas transport properties were studied. The nanodispersed inorganic network produced in the organic matrix was characterized by solid-state 29 Si NMR, Fourier transform infrared (FT-IR), dynamic light scattering (DLS) and field emission scanning electron microphotography (FE-SEM). Wide angle X-ray diffraction (WAXD) patterns and differential scanning calorimetry (DSC) thermograms of PEBAX ® and hybrid materials revealed that the incorporation of silica induced the structural modification of polymer chains. Gas Permeation measurements were accomplished at various temperatures with He, CO 2 , O 2 and N 2 . These hybrid membranes exhibited higher Gas permeability coefficients and permselectivities than PEBAX ® , particularly at an elevated temperature. Activation energy of CO 2 Permeation through the hybrid membranes decreased due to the large contribution of heat of sorption while that of N 2 increased resulting from the increase of tortuosity and restricted chain mobility. All these results were explained by the increase of sorption ability of hybrids, attributed to the strong interaction between CO 2 molecules and SiO 2 domains, additional sorption sites in polyamide block in PEBAX ® and the organic/inorganic interphase.
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Gas Permeation of poly amide 6 b ethylene oxide copolymer
2001Co-Authors: Jaehoon Kim, Young Moo LeeAbstract:Abstract Block copolymers exhibit a different Gas Permeation behavior from that of homopolymers. In the diffusion process, the fraction of impermeable regions in the block copolymer decreases the diffusivity and the permeability. As the amount of impermeable regions in the block copolymer increases, the flow paths for the Gas diffusion are restricted. Poly(amide-6-b-ethylene oxide) (PEBAX®) copolymer consists of a regular linear chain of rigid polyamide for hard segment interspaced with flexible polyether for soft segment. PEBAX® copolymer shows a typical Permeation behavior of rubbery polymers. The permeability of CO2 increases with the pressure originating from the increment of the sorbed CO2 amounts. PEBAX® copolymer shows the high permeability and the high selectivity for polarizable/nonpolar Gas pairs. Particularly, the selectivity of CO2 over N2 is 61 and that of SO2 over N2 is 500. For small and nonpolar Gases (i.e. He, H2, O2 and N2), the permeability decreases with increasing the molecular size or volume of Gases. On the other hand, for polarizable and larger Gases (i.e. CO2 and SO2), it shows the high permeability. The high permeability and permselectivity of PEBAX® copolymer are attributed of polarizable Gases to polyether segment in PEBAX®.
Ludmila Starannikova - One of the best experts on this subject based on the ideXlab platform.
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synthesis and Gas Permeation properties of novel spirobisindane based polyimides of intrinsic microporosity
2013Co-Authors: Yulia Rogan, Ludmila Starannikova, Yuri Yampolskii, V Ryzhikh, Paola Bernardo, Fabio Bazzarelli, J C Jansen, Neil B MckeownAbstract:Three novel polyimides (PIM-PIs) with characteristics similar to a polymer of intrinsic microporosity (PIM) were prepared by the reactions of a novel spirobisindane-based dianhydride with appropriate aromatic diamines. A polymerisation procedure via in situ ester precursor formation provided PIM-PIs with very high molar masses. The Gas Permeation parameters (permeability (P), diffusion (D) and solubility (S) coefficients) were determined for these polymers. These PIM-PIs exhibit both high apparent surface areas and high Gas permeability coefficients, greater than those of most polyimides studied so far and only slightly smaller than the permeability coefficients of the archetypal polymer of intrinsic microporosity, PIM-1. Treatment of the films with alcohols results in significant increases the P values, just as has been noted for PIM-1. This enhancement is caused by an increase of the diffusion coefficients, while the solubility coefficients are much less sensitive to this treatment. However, PIM-PIs are distinguished by extremely high Gas solubility coefficients a property, which is characteristic to all PIMs.
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Gas Permeation parameters of mixed matrix membranes based on the polymer of intrinsic microporosity pim 1 and the zeolitic imidazolate framework zif 8
2013Co-Authors: Alexandra F Bushell, Peter M Budd, Ludmila Starannikova, Yuri Yampolskii, Paola Bernardo, Fabio Bazzarelli, Martin P Attfield, Christopher R Mason, Alexander Rebrov, J C JansenAbstract:Abstract Mixed matrix membranes (MMMs) based on the polymer of intrinsic microporosity PIM-1 and the zeolitic imidazolate framework ZIF-8 were prepared and their Permeation and sorption properties investigated. Self-supported films with ZIF-8 contents up to 43 vol% were studied using GC Gas Permeation apparatus and a McBain sorption microbalance. Permeability coefficients were determined for the following set of Gases: He, H 2 , O 2 , N 2 , CO 2 , CH 4 . For “as-cast” films, an increase in ZIF-8 loading results in increases in the permeability and diffusion coefficients as well as in the separation factors α (H 2 /N 2 ), α (H 2 /CH 4 ), α (He/N 2 ), α (O 2 /N 2 ) and α (CO 2 /CH 4 ). For all ZIF-8 contents studied, permeability is enhanced by treatment with ethanol. Data points on several Robeson diagrams are located above the 2008 upper bound. Free volume in MMMs containing ZIF-8 was studied using positron annihilation lifetime spectroscopy (PALS) and radio thermoluminescence (RTL) methods. It was shown that the introduction of ZIF-8 nanoparticles into the PIM-1 matrix results in an increase in free volume which may be assumed to arise from a combination of the contributions cavities and of more loosely packed polymer chains at the boundary between ZIF-8 particles and the PIM-1 matrix. The results obtained for the PIM-1/ZIF-8 MMMs are compared with literature data for other MMMs.
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synthesis characterization and Gas Permeation properties of a novel group of polymers with intrinsic microporosity pim polyimides
2009Co-Authors: Bader Ghanem, Neil B Mckeown, Peter M Budd, Nasser M Alharbi, Detlev Fritsch, Kathleen Heinrich, Ludmila Starannikova, Andrei Tokarev, Yuri YampolskiiAbstract:A range of polyimides with characteristics similar to a polymer of intrinsic microporosity (PIM) were prepared by reaction with various aromatic diamines of a bis(carboxylic anhydride) incorporating a spiro-center. The polymers exhibited high surface area, as determined by nitrogen adsorption, and high thermal stability. Membrane Gas Permeation experiments showed PIM-polyimides to be among the most permeable of all polyimides and to have selectivities close to the upper bound for several important Gas pairs. A group contribution method was used to predict permeability coefficients and separation factors for further PIM-polyimide structures, revealing worthwhile targets for future synthetic efforts.
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Gas Permeation parameters and other physicochemical properties of a polymer of intrinsic microporosity polybenzodioxane pim 1
2008Co-Authors: Peter M Budd, Bader Ghanem, Neil B Mckeown, Detlev Fritsch, Ludmila Starannikova, Yuri Yampolskii, Kadhum J Msayib, N A Belov, Olga Sanfirova, V P ShantarovichAbstract:Abstract A detailed study of Gas Permeation, thermodynamic properties and free volume was performed for a novel polymer of intrinsic microporosity (PIM-1). Gas permeability was measured using both Gas chromatographic and barometric methods. Sorption of vapors was studied by means of inverse Gas chromatography (IGC). In addition, positron annihilation lifetime spectroscopy (PALS) was employed for investigation of free volume in this polymer. An unusual property of PIM-1 is a very strong sensitivity of Gas permeability and free volume to the film casting protocol. Contact with water in the process of film preparation resulted in relatively low Gas permeability ( P (O 2 ) = 120 Barrer), while soaking with methanol led to a strong increase in Gas permeability ( P (O 2 ) = 1600 Barrer) with virtually no evidence of fast aging (decrease in permeability) that is typical for highly permeable polymers. For various Gas pairs (O 2 /N 2 , CO 2 /CH 4 , CO 2 /N 2 ) the data points on the Robeson diagrams are located above the upper bound lines. Hence, a very attractive combination of permeability and selectivity is observed. IGC indicated that this polymer is distinguished by the largest solubility coefficients among all the polymers so far studied. Free volume of PIM-1 includes relatively large microcavities ( R = 5 A), and the results of the PALS and IGC methods are in reasonable agreement.
Ulrich W Suter - One of the best experts on this subject based on the ideXlab platform.
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epoxy layered silicate nanocomposites and their Gas Permeation properties
2004Co-Authors: Maged A Osman, Vikas Mittal, Massimo Morbidelli, Ulrich W SuterAbstract:Epoxy-OM (organo-montmorillonite) nanocomposites have been synthesized, and their permeability to oxygen and water vapor has been measured. The chemical structure of the organic monolayer ionically bonded to the montmorillonite surface has been varied, and its influence on the swelling, intercalation, and exfoliation behavior of the OM has been studied. Exfoliated aluminosilicate layers build a barrier for the permeating Gas molecules, while the polymer intercalated tactoids do not contribute much to the Permeation barrier performance. The Gas Permeation through the composites was correlated to the volume fraction of the impermeable inorganic part of the OM. The incorporation of small volume fractions of the platelike nanoparticles in the polymer matrix decreased its permeability coefficient when the interface between the two heterogeneous phases was properly designed. Long alkyl chains enhanced the polymer intercalation but increased the permeability coefficient probably due to phase separation at the in...
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polyurethane adhesive nanocomposites as Gas Permeation barrier
2003Co-Authors: Maged A Osman, Vikas Mittal, Massimo Morbidelli, Ulrich W SuterAbstract:Adhesive nanocomposites of organically modified montmorillonite (OM) and polyurethane have been synthesized and their permeability to oxygen and water vapor has been measured. The Gas Permeation through the composites was correlated to the volume fraction of the impermeable inorganic part of the OM. The incorporation of small volume fractions of the platelike nanoparticles in the polymer matrix decreased the Gas transmission rate, when the interface between the two heterogeneous phases was properly designed. The oxygen transmission rate decayed asymptotically with increasing aluminosilicate volume fraction and a 30% reduction was achieved at 3 vol %, when the clay was coated with bis(2-hydroxyethyl) hydrogenated tallow ammonium or alkylbenzyldimethylammonium ions. In contrast, coating the clay surface with dimethyl dihydrogenated tallow ammonium ions leads to an increase in the Gas transmission rate with augmenting inorganic fraction. This was attributed to a probable change in morphology resulting from phase separation at the interface between the apolar pure hydrocarbon clay coating and the relatively polar PU. The water vapor Permeation through the PU nanocomposites was more strongly reduced than oxygen and a 50% reduction was observed at 3 vol % silicate fraction. This was attributed to stronger interactions and hydrogen bonding of the water molecules with the PU matrix as well as to their clustering. Differences in the hydrophobicity of the clay coating influenced the water transmission rate. No spectroscopic evidence could be obtained for a reaction between the hydroxyl groups of the clay organic coating and the isocyanate groups of the prepolymer. A mixed morphology, that is, exfoliated layers and intercalated particles was observed in all composites. WAXRD and TEM gave a qualitative picture of the microstructure of the nanocomposites but no conclusive information. Some of the problems to be solved before a correlation between the nanocomposite properties and their microstructure can be established have been outlined.
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polyurethane adhesive nanocomposites as Gas Permeation barrier
2003Co-Authors: Maged A Osman, Vikas Mittal, Massimo Morbidelli, Ulrich W SuterAbstract:Adhesive nanocomposites of organically modified montmorillonite (OM) and polyurethane have been synthesized and their permeability to oxygen and water vapor has been measured. The Gas Permeation through the composites was correlated to the volume fraction of the impermeable inorganic part of the OM. The incorporation of small volume fractions of the platelike nanoparticles in the polymer matrix decreased the Gas transmission rate, when the interface between the two heterogeneous phases was properly designed. The oxygen transmission rate decayed asymptotically with increasing aluminosilicate volume fraction and a 30% reduction was achieved at 3 vol %, when the clay was coated with bis(2-hydroxyethyl) hydrogenated tallow ammonium or alkylbenzyldimethylammonium ions. In contrast, coating the clay surface with dimethyl dihydrogenated tallow ammonium ions leads to an increase in the Gas transmission rate with augmenting inorganic fraction. This was attributed to a probable change in morphology resulting from phase separation at the interface between the apolar pure hydrocarbon clay coating and the relatively polar PU. The water vapor Permeation through the PU nanocomposites was more strongly reduced than oxygen and a 50% reduction was observed at 3 vol % silicate fraction. This was attributed to stronger interactions and hydrogen bonding of the water molecules with the PU matrix as well as to their clustering. Differences in the hydrophobicity of the clay coating influenced the water transmission rate. No spectroscopic evidence could be obtained for a reaction between the hydroxyl groups of the clay organic coating and the isocyanate groups of the prepolymer. A mixed morphology, that is, exfoliated layers and intercalated particles was observed in all composites. WAXRD and TEM gave a qualitative picture of the microstructure of the nanocomposites but no conclusive information. Some of the problems to be solved before a correlation between the nanocomposite properties and their microstructure can be established have been outlined.
