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Four spirobichroman-based polyimides (6FDA-F, 6FDA-O, 6FDA-P, and 6FDA-M) were successfully obtained via polyreaction between diamines of different substituents (-H, -OCH3, -N, and -CH3) and 4,4′-(hexafluoroisopropylidene)-diphthalic anhydride (6FDA). The molecular weights, thermophysical, dihedral angle of the molecules, fractional free volume, d-spacing, Brunauer–Emmett–Teller surface area, and gas separation performance were studied through a combination of experiments and molecular dynamics simulations. These polymers show high molecular weights, with number-average molecular weights (Mn) in the range of 5.0–15.3 × 104, and excellent thermal stability, with weight loss temperatures (T5%) of over 420 °C. The pure-gas (O2, N2, CO2, and CH4) permeation results indicated that the four polymers selectivity of CO2/CH4 over 31 and that 6FDA-F had the highest gas permeability among the four tested gases. Importantly, the dihedral angle from molecular simulation was used to clarify the phenomenon wherein the 6FDA-P gas permeability lower than 6FDA-F. A detailed analysis indicates that -CH3 increased the gas permeability of the polyimides, while the turnstile-like rotary thermal motion of -OCH3 formed channel obstacles and improved the gas selectivity. The polymers containing pyridine ring and those containing benzene ring follows different gas separation mechanisms, based on the gas solution-diffusion behaviour.

In this work, the behavior of new GO-based mixed matrix membranes was tested in view of their use as CO2-selective membrane in post combustion carbon capture applications. In particular, the new materials were obtained by mixing of Pebax&reg, 2533 copolymer with different types of graphene oxide (GO). Pebax&reg, 2533 has indeed lower selectivity, but higher permeability than Pebax&reg, 1657, which is more commonly used for membranes, and it could therefore benefit from the addition of GO, which is endowed with very high selectivity of CO2 with respect to nitrogen. The mixed matrix membranes were obtained by adding different amounts of GO, from 0.02 to 1% by weight, to the commercial block copolymers. Porous graphene oxide (PGO) and GO functionalized with polyetheramine (PEAGO) were also considered in composites produced with similar procedure, with a loading of 0.02%wt. The obtained films were then characterized by using SEM, DSC, XPS analysis and permeability experiments. In particular, permeation tests with pure CO2 and N2 at 35&deg, C and 1 bar of upstream pressure were conducted for the different materials to evaluate their separation performance. It has been discovered that adding these GO-based nanofillers to Pebax&reg, 2533 matrix does not improve the ideal selectivity of the material, but it allows to increase CO2 permeability when a low filler content, not higher than 0.02 wt%, is considered. Among the different types of GO, then, porous GO seems the most promising as it shows CO2 permeability in the order of 400 barrer (with an increase of about 10% with respect to the unloaded block copolymer), obtained without reducing the CO2/N2 selectivity of the materials, which remained in the order of 25.

High-flux nanoporous single-layer graphene membranes are highly promising for energy-efficient gas separation. Herein, in the context of carbon capture, a remarkable enhancement in the CO(2)selectivity is demonstrated by uniquely masking nanoporous single-layer graphene with polymer with intrinsic microporosity (PIM-1). In the process, a major bottleneck of the state-of-the-art pore-incorporation techniques in graphene has been overcome, where in addition to the molecular sieving nanopores, larger nonselective nanopores are also incorporated, which so far, has restricted the realization of CO2-sieving from graphene membranes. Overall, much higher CO2/N(2)selectivity (33) is achieved from the composite film than that from the standalone nanoporous graphene (NG) (10) and the PIM-1 membranes (15), crossing the selectivity target (20) for postcombustion carbon capture. The selectivity enhancement is explained by an analytical gas transport model for NG, which shows that the transport of the stronger-adsorbing CO(2)is dominated by the adsorbed phase transport pathway whereas the transport of N(2)benefits significantly from the direct gas-phase transport pathway. Further, slow positron annihilation Doppler broadening spectroscopy reveals that the interactions with graphene reduce the free volume of interfacial PIM-1 chains which is expected to contribute to the selectivity. Overall, this approach brings graphene membrane a step closer to industrial deployment.

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. Carboxylate-functionalised polymers of intrinsic microporosity (C-PIMs) are highly desirable materials for membrane separation applications. The recently reported method to afford C-PIMs was via an extensive base hydrolysis process requiring 360 h. Herein, a novel and effective method to convert PIM-CONH2 to C-PIM using nitrous acid was studied. The chemical structure of C-PIM was characterised by1H NMR,13C NMR, FTIR, elemental analysis, UV-Vis, TGA and TGA-MS. Complete conversion from amide to carboxylic acid groups was confirmed. Decarboxylation of C-PIM was also successfully studied by TGA-MS for the first time, with a loss of m/z 44 amu (CO2) observed at the first degradation stage. TGA also revealed decreased thermal stability of C-PIM relative to PIM-CONH2 under both N2 and air atmosphere. Gel permeation chromatography (GPC) analysis showed continuous molecular weight degradation of C-PIM with extended reaction time. Aromatic nitration was also observed as a side reaction in some cases.

European Union's Seventh Framework Program (FP7/2007-2013) under Grant agreement no. 608490. project M4CO2. CNR/FCT Italian/Portuguese Bilateral Project 2015-2016 "Advanced studies of the transport properties and gas separation by polymers of intrinsic microporosity (PIMs) and Ionic Liquid Gel Membranes via novel methods" and the CNR-CAS Bilateral Agreement 2016-2018 "Innovative polymeric membranes for pervaporation and advanced gas and vapour separations". A novel method to determine the individual diffusion coefficients of gases in a mixture during their permeation through polymeric membranes is described. The method was developed in two independent laboratories, using rubbery Pebax® and glassy Hyflon® AD60X membrane samples as standards, and validated using the Tröger's base containing Polymer of Intrinsic Microporosity, PIM-EA-TB. Monitoring of the permeate composition in real time by a quadrupole mass spectrometer allowed the analysis of the permeation transient for gas mixtures. Two operation modes, either with a vacuum in the permeate and a direct connection to the mass spectrometer via a heated restriction, or using a sweeping gas and a heated capillary sample inlet, give excellent agreement with the traditional time lag method for single gases. A complete overview of the method development, identification of the critical parameters, instruments calibration, data elaboration and estimation of the experimental accuracy are provided. Validation with PIM-EA-TB, shows that the method can also successfully detect anomalous phenomena, related to pressure and concentration dependency of the transport properties, physical aging or penetrant-induced dilation. Rapid online analysis of the permeate composition makes the method also very suitable for routine mixed gas permeability measurements. publishersversion published

In gas separation membrane processes, CO2 may induce the plasticization of glassy polymer, lowering its the mechanical rigidity and reducing the glass transition, with a loss of separation performances. Such mechanism is often associated to gas permeability behavior in glassy membranes vs. upstream p, and increasing trends are considered as the footprint of the plasticization onset. However, there is no clear correlation between gas permeability and the effects of CO2 on mechanical behavior. The CO2 induced plasticization in glassy membranes is investigated by direct DMA analysis of polymers saturated at different CO2 pressures. Matrimid polyimide is considered, as it shows a non-monotonous CO2 permeability behavior, and compared to PS (decreasing behavior) and PMMA (increasing).CO2 lowed the elastic modulus of all materials investigated, while the relaxation dynamics revealed a strong enhancement of tan δ, even in absence of a second order transition. The same qualitative behaviors are observed for all glassy systems investigated, and in Matrimid, no apparent change is identified around the pressure value corresponding to the minimum in CO2 permeability, excluding the presence of a new phenomenon onset. Results suggest that increasing permeability behaviors and non-monotonous trends, are not directly related to softening effect induced by CO2 in the polymer matrix, and such features have to be ascribed to the combination of solubility and diffusivity coefficients.In gas separation membrane processes, CO2 may induce the plasticization of glassy polymer, lowering its the mechanical rigidity and reducing the glass transition, with a loss of separation performances. Such mechanism is often associated to gas permeability behavior in glassy membranes vs. upstream p, and increasing trends are considered as the footprint of the plasticization onset. However, there is no clear correlation between gas permeability and the effects of CO2 on mechanical behavior. The CO2 induced plasticization in glassy membranes is investigated by direct DMA analysis of polymers saturated at different CO2 pressures. Matrimid polyimide is considered, as it shows a non-monotonous CO2 permeability behavior, and compared to PS (decreasing behavior) and PMMA (increasing).CO2 lowed the elastic modulus of all materials investigated, while the relaxation dynamics revealed a strong enhancement of tan δ, even in absence of a second order transition. The same qualitative behaviors are observed for all g...

Two series of novel aromatic polyimides (PIs) containing three polymers each one were prepared using two new aromatic silylated-diamine monomers. These monomeric diamines contain biphenylsilane units and biphenyl moieties in their structures. All PIs were obtained in high yield and the inherent viscosities were in the range of 0.44 to 0.82 dL/g. Polyimides showed excellent solubility in a wide variety of aprotic polar solvents, including THF and chloroform and were thermally stable with thermal decomposition temperature (TDT) over 500 °C and high glass transition temperatures (Tg) between 230 and 270 °C. Additionally, two films were prepared and gas transport properties were determined. These films offered a reasonably acceptable balance of permeability and selectivity with values close to a commercial polyimide (Matrimid), in particular for the CO/N gases pair. Experimental density of the films was measured and the fractional free volume was calculated., Tundidor-Camba, A. acknowledges the financial assistance by Fondo Nacional de Investigación Científica y Tecnológica, FONDECYT, through Project 11140133 and kindly thanks Cristina Álvarez for helping with the measurements of gas permeability.

Gas separation membranes, considered among one of the promising emerging capture technologies for post-combustion capture, requires a two-stage process with significant compression work for CO2 capture from a coal fired power plant flue gas. A hybrid membrane–liquefaction process for post-combustion CO2 capture from the power plant flue gas is developed to mitigate the deficiencies of the two-stage membrane process. The energy efficiency of the process depends on the permeate CO2 composition from the membrane unit. The performance envelope of the hybrid process is evaluated and shows that the optimum CO2 concentration in the permeate is 65%– 67% depending on the targeted CCR. A techno-economic analysis for 85% CCR was performed and the cost of CO2 avoided is calculated to 48 €2008/tCO2,avoided, that is, 9% more cost-efficient than the baseline MEA absorption process.

Poly(1-trimethylsilyl-1-propyne) (PTMSP) is one of the most gas permeable polymers among all the synthetic polymers. Its oxygen permeability coefficient (Po2) reaches up to about 10 000 barrers. It is known that the gas permeability of PTMSP decreases with time, but the details are not clear yet. In the present study, the time dependence of the gas permeability of PTMSP was examined by storing the membrane sample under three deferent conditions ; (1) in a sealed polyethylene suck, (2) in air, and (3) in a vacuum drying oven. Consequently the extent of decrease of gas permeability increased in the older of (1)

Poly(1-trimethylsilyl-1-propyne) (PTMSP) is one of the most gas permeable polymers among all the synthetic polymers. Its oxygen permeability coefficient (Po2) reaches up to about 10 000 barrers. It is known that the gas permeability of PTMSP decreases with time, but the details are not clear yet. In the present study, the time dependence of the gas permeability of PTMSP was examined by storing the membrane sample under three deferent conditions ; (1) in a sealed polyethylene suck, (2) in air, and (3) in a vacuum drying oven. Consequently the extent of decrease of gas permeability increased in the older of (1)

This work presents the results of a process of optimization applied to gadolinia-doped ceria (Ce0.8Gd0.2O1.9-x, or CGO) thin films, deposited by spray pyrolysis (SP). Spray pyrolysis is a high thermal deposition method that combines material deposition and heat treatment. This combination is advantageous since the post-deposition heat treatment step is not necessary. However, stresses are solidified in the coating during the deposition, which may lead to the initiation of a crack in the coating. The aim of this work was to achieve thin, dense, and continuous CGO coatings, which may be used as gas separation membranes and as a solid state electrochemical interfaces. Dense, flat, low-defect substrates such as silica slides, silicon mono crystal wafers, and porous substrates were used as substrates in this work. Cerium ammonium nitrate and gadolinium acetylacetonate were dissolved in ethanol and butyl carbitol to form a precursor solution that was sprayed on the heated substrates. Process parameters such as solvent composition, deposition rate and different heating regimes were analyzed. The microstructure was analyzed by secondary electron microscopy (SEM) and was found that thin, dense, and defect-free films could be produced on dense and porous substrates. The results obtained show that it is possible to obtain a CGO dense film deposited by spray pyrolysis. X-ray diffraction (XRD) analysis showed that the films were crystalline after the deposition without requiring post-deposition heat treatment. The crystallite size does not vary significantly as a function of the annealing temperature. © 2012 Elsevier Ltd.

Certain polyacetylenes having spherical substituents are known to exhibit high gas permeability. Poly[1-phenyl-2-(p-trimethylsilyl)phenylacetyllene] (PTMSDPA) is one of such examples, and its oxygen permeability coefficient (PO2) has been reported to be about 1500 barrers. Though poly(1-trimethylsilyl-1-propyne) is known to be most permeable among all the existing polymers, its gas permeability remarkably decreases with time. The purpose of the present study is to elucidate the time dependence of gas permeability of PTMSDPA. The initial values of PO2 and PN2 were determined to be 2200 and 1000 barrers. Further it was clarified that the gas permeability of PTMSDPA hardly changed even after six weeks irrespective of the method of preservation.

Certain polyacetylenes having spherical substituents are known to exhibit high gas permeability. Poly[1-phenyl-2-(p-trimethylsilyl)phenylacetyllene] (PTMSDPA) is one of such examples, and its oxygen permeability coefficient (PO2) has been reported to be about 1500 barrers. Though poly(1-trimethylsilyl-1-propyne) is known to be most permeable among all the existing polymers, its gas permeability remarkably decreases with time. The purpose of the present study is to elucidate the time dependence of gas permeability of PTMSDPA. The initial values of PO2 and PN2 were determined to be 2200 and 1000 barrers. Further it was clarified that the gas permeability of PTMSDPA hardly changed even after six weeks irrespective of the method of preservation.

This paper describes an investigation for multi-stage systems used in coal-fired power plant. The whole work was divided into two steps: energetic and economic analyses. In the first step: on the basis of a serial concept, through varying the position of compressors and vacuum pumps, recycling the retentate of the 2nd membrane to the feed side of the 1st membrane, a cascade variant was developed and analysed. In the second step: an economic model was developed to calculate the capture cost of the cascade system. The total cost is composed of investment cost, operation and maintenance (O&M) cost and electricity cost. A correlation between the membrane parameters: selectivity & permeability and capture performance: energy consumption & capture cost was built up. Using Polyactive® membrane developed by GKSS with CO2 permeance of 3 Nm3/m2hbar and CO2/N2 selectivity of 50, under the separation target of 70% degree of CO2 separation and 95 mol% CO2 purity, adopting the cascade membrane system in the 600 MW NRW-reference power plant, the specific energy consumption including CO2 compression (110 bar, 30 °C) is 256 kWh/tseparatedCO2 with 6.4%-pts efficiency loss. The capture cost is 31 euro/tseparatedCO2, which could be a promising solution as a retrofit for the existing power plants.

This work reports on the preparation and gas transport performance of mixed matrix membranes (MMMs) based on the polymer of intrinsic microporosity (PIM-1) and potassium dodecahydrododecaborate (K2B12H12) as inorganic particles (IPs). The effect of IP loading on the gas separation performance of these MMMs was investigated by varying the IP content (2.5, 5, 10 and 20 wt %) in a PIM-1 polymer matrix. The derived MMMs were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), single gas permeation tests and sorption measurement. The PIM1/K2B12H12 MMMs show good dispersion of the IPs (from 2.5 to 10 wt %) in the polymer matrix. The gas permeability of PIM1/K2B12H12 MMMs increases as the loading of IPs increases (up to 10 wt %) without sacrificing permselectivity. The sorption isotherm in PIM-1 and PIM1/K2B12H12 MMMs demonstrate typical dual-mode sorption behaviors for the gases CO2 and CH4.

It was previously reported that CO2 could be reformed into CO, CH4, etc., which can be used as fuels, by TiO2 as the photocatalyst and under UV radiation. If this technique could be applied practically, a carbon circulation system would then be able to be constructed by reforming CO2 from combustion, using solar energy, to fuel, which would solve the problem of global warming and fossil fuels depletion all together. However, the technology is not yet practicable as the fuel concentration of products is too low. To increase the concentration and improve CO2 reforming performance on TiO2, a membrane reactor composed of TiO2 and gas separation membrane prepared by sol–gel and dip-coating method has been built. Study on the factors influencing membrane performance, e.g. rising speed in the dip-coating process, has been carried out with the reactor. The results of the study are reported in this paper.

This paper describes a detailed process optimization of the mass and energy balances for multi-stage membrane systems used in coal-fired power plants. Based on the recovery rate of 50% or 90% CO 2 with 95 mol% CO 2 purity, different concepts using recirculation of flue gas and variation of feed gas compressor and vacuum pump on the permeate side were developed and optimized to obtain minimum energy consumption. Simultaneously, a cost model was developed to make a further analysis of the optimized concept in view of the tradeoff balance between material and energy consumption.

This dissertation focuses on the synthesis and characterization of high performance polymers, especially polyimides, polybenzoxazoles and polybenzimidazoles for gas separation applications. An abundance of monomers and novel polymers were synthesized and fabricated into membranes. Thermally rearranged polybenzoxazoles and their precursor polyimides were systematically studied with regard to size of pendant functional groups, thermal rearrangement conversion, and relationship of backbone structure/gas transport properties. 3,3'-Diamino-4,4'-dihydroxybiphenyl was synthesized using an economical route. Meta and para oriented polyimides with different ortho-functionality were synthesized and these polymers were thermally rearranged into polybenzoxazoles. The polar hydroxyl functional groups on the polyimide backbone diminished the meta/para isomer effect of the permeability coefficients of the polymers and only a small difference between meta- and para-oriented polyhydroxyimides in permeability coefficients was observed. The TR polybenzoxazoles derived from meta/para-oriented isomeric polyimides with ortho functionality had similar gas separation properties, especially for CO2/CH4 separation, and it is hypothesized that this is due to a lack of intersegmental mobility distinction between the two isomeric TR polymers. The TR polymers derived from the polyimides with acetate ortho-functional groups had significantly better gas separation properties than ones derived from the precursor with hydroxyl ortho-functional groups. Polybenzimidazoles were also investigated for use as gas separation membranes. Polybenzimidazoles are some of the most thermally stable polymers. However, commercial polybenzimidazoles do not have good solubility in common solvents. The solubility issue was solved by incorporating sulfonyl linkages into the polybenzimidazole backbone using a 3,3',4,4'-tetraaminodiphenylsulfone (TADPS) monomer. 3,3',4,4'-Tetraaminodiphenylsulfone was synthesized by a novel route with higher overall yield and less steps than the traditional synthetic method. The TADPS based polybenzimidazoles also demonstrated better thermal stability than commercial polybenzimidazole. The meta/para oriented isomer effect on gas transport properties is discussed. TADPS-based polybenzimidazoles exhibited H2/CO2 gas separation properties near or surpassing the upper bound with H2 permeabilities from 3.6 to 5.7 Barrer and selectivities from 10.1 to 32.2 at 35 °C. Ph. D.

Membrane gas separations require materials with high permeability and good selectivity. For glassy polymers, the gas transport properties depend strongly on the amount and distribution of free volume, which may be enhanced either by engineering the macromolecular backbone to frustrate packing in the solid state or by thermal conversion of a soluble precursor to a more rigid structure of appropriate topology. The first approach gives polymers of intrinsic microporosity (PIMs), while the second approach is used in thermally rearranged (TR) polymers. Recent research has sought to combine these approaches, and here a new range of thermally rearrangeable PIM-polyimides are reported, derived from dianhydrides incorporating a spiro center. Hydroxyl-functionalized polyimides were prepared using two different diamines: 2,2-bis(3-amino-4-hydroxyphenyl) hexafluoropropane (bisAPAF) and 4,6-diaminoresorcinol (DAR). Thermal treatment at 450 °C under N2 for 1 h yielded polybenzoxazole (PBO) polymers, which showed increased permeability, compared to the precursor, in membrane gas permeation experiments. A polymer based on DAR (PIM-PBO-3) exhibited a CO2/N2 selectivity of 30 as prepared, higher than the values of 21-23 obtained for polymers derived from bisAPAF with the same dianhydride (PIM-PBO-1). © 2014 American Chemical Society.

Since the first report of the synthesis of poly[1-(trimethylsilyl)-1-propyne] [poly(TMSP)] in 1983, a large number of publications, presently up to about 350 journal articles and patents, has appeared due to its unique structure and properties and, in particular, its extremely high gas permeability. This review article surveys the synthesis, properties, and functions of poly(TMSP) and related polymers. Investigations of all aspects of this polymer are introduced: journal articles are cited comprehensively, and important patents are included. Poly(TMSP) can be obtained by metathesis polymerization of 1-(trimethylsilyl)-1-propyne by TaCl5 and NbCl5. This polymer is characterized by high molecular weight (up to around one million), good solubility in many common solvents (e.g. toluene and chloroform), formation of tough films by solution casting, a high glass transition temperature (>250°C), and fair thermal stability. Its oxygen permeability at 25°C is ca. 6×10−7 cm3(STP)cm/(cm2 s cmHg), which is the highest value of all existing polymers. The gas permeation properties of poly(TMSP) have been intensively studied, especially with regard to various permeation mechanisms. Various modifications of poly(TMSP) have also been examined to improve its gas separation performance. Other applications which have been investigated for poly(TMSP) include pervaporation (as an ethanol–water separation membrane), sensors, and photoresists.

Membrane processes are gaining an increasingly important role in industrial gas separation processes [1]. Gas transport in polymeric membranes is governed by the well know solution-diffusion mechanism, in which the permeability, P, is the product of the solubility and the diffusivity of the permeating species in the polymer matrix. Consequently, also the selectivity, ?ij, between the two species i and j is composed of a solution term and a diffusion term. The design and development of novel membrane materials should take into account the individual contributions of both terms, which often appear to be contrasting one another. In dense and very stiff materials, such as glassy polymers, the diffusion of large molecules is penalized, thus such membranes are predominantly size-sieving. Due to the much faster diffusion, such membranes are hydrogen selective and this behavior can be further enhanced by cross-inking of the polymer phase [2]. In liquid or rubbery membranes, the diffusion rate of all species is comparable and the selectivity is dominated by the difference in solubility of the gas species present in the mixture. Room temperature ionic liquids are liquid salts with negligible vapor tension and this makes them suitable for liquid membranes [3]. Tailoring of the polymer gels based on ionic liquids were recently found to give remarkably high CO2 over hydrogen selectivity at high IL content [4].Polymers of intrinsic microporosity [5] are known to have high solubility of readily condensable species, while they promote fast diffusion due to their high free volume and interconnected void structure. Under specific conditions such materials can also be given relatively high diffusion selectivity [6]. In the present paper we will explore the various approaches to purify hydrogen, either by its enrichment in the permeate stream in hydrogen selective membranes, or by its concentration in the retentate stream through selective removal of heavier species.

Hybrid membranes represent a promising alternative to the limitations of organic and inorganic materials for high productivity and selectivity gas separation membranes. In this study, the previously developed concept of emulsion-polymerized mixed matrix (EPMM) membranes was further advanced by investigating the effects of surfactant and compatibilizer on inorganic loading in poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)-based EPMM membranes, in which inorganic part of the membranes originated from tetraethylorthosilicate (TEOS). The polymerization of TEOS, which consists of hydrolysis of TEOS and condensation of the hydrolyzed TEOS, was carried out as (i) one- and (ii) two-step processes. In the one-step process, the hydrolysis and condensation take place in the same environment of a weak acid provided by the aqueous solution of aluminum hydroxonitrate and sodium carbonate. In the two-step process, the hydrolysis takes place in the environment of a strong acid (solution of hydrochloric acid), whereas the condensation takes place in weak base environment obtained by adding excess of the ammonium hydroxide solution to the acidic solution of the hydrolyzed TEOS. For both one- and two-step processes, the emulsion polymerization of TEOS was carried out in two types of emulsions made of (i) pure trichloroethylene (TCE) solvent, and (ii) 10 w/v% solution of PPO in TCE, using different combinations of the compatibilizer (ethanol) and the surfactant (n-octanol). The experiments with pure TCE, which are referred to as a gravimetric powder method (GPM) allowed assessing the effect of different experimental parameters on the conversion of TEOS. The GPM tests also provided a guide for the synthesis of casting emulsions containing PPO, from which the EPMM membranes were prepared using a spin coating technique. The synthesized EPMM membranes were characterized using 29Si nuclear magnetic resonance (29Si NMR), differential scanning calorimetry (DSC), inductively coupled plasma mass spectrometry (ICP-MS), and gas permeation measurements carried out in a constant pressure (CP) system. The 29Si NMR analysis verified polymerization of TEOS in the emulsions made of pure TCE, and the PPO solution in TCE. The conversions of TEOS in the two-step process in the two types of emulsions were very close to each other. In the case of the one-step process, the conversions in the TCE emulsion were significantly greater than those in the emulsion of the PPO solution in TCE. Consequently, the conversions of TEOS in the EPMM membranes made in the two-step process were greater than those in the EPMM membranes made in the one-step process. The latter ranged between 10 - 20%, while the highest conversion in the two-step process was 74% in the presence of pure compatibilizer with no surfactant. Despite greater conversions and hence the greater inorganic loadings, the EPMM membranes prepared in the two-step process had glass transition temperatures (Tg) only slightly greater than the reference PPO membranes. In contrast, despite relatively low inorganic loadings, the EPMM membranes prepared in the one-step process had Tgs markedly greater than PPO, and showed the expected trend of an increase in Tg with the inorganic loading. These results indicate that in the case of the one-step process the polymerized TEOS was well integrated with the PPO chains and the interactions between the two phases lead to high Tgs. On the other hand, this was not the case for the EPMM membranes prepared in the two-step process, suggesting possible phase separation between the polymerized TEOS and the organic phase. The latter was confirmed by detecting no selectivity in the EPMM membranes prepared by the two-step process. In contrast, the EPMM membranes prepared in the one-step process in the presence of the compatibilizer and no surfactant showed 50% greater O2 permeability coefficient and a slightly greater O2/N2 permeability ratio compared to the reference PPO membranes.

Emulsion polymerized mixed matrix (EPMM) membranes is a new category of membranes, which incorporate silica-based inorganic nanoparticles dispersed in continuous phase of an organic polymer. The uniqueness of the EPMM membranes comes from the fact that they may combine otherwise incompatible inorganic and organic phases. This is achieved by the synthesis of the inorganic nanoparticles from a silica precursor in a stable emulsion, in which an aqueous phase is dispersed in a continuous phase of the polymer solution. More specifically, the silica precursor soluble in the polymer solution polymerizes in contact with the aqueous phase, and consequently the latter acts as finely dispersed micro reactors. The objective of this work was to optimize the previously developed protocol for the synthesis of poly (2,6-dimethyl-1,4pheneylene oxide) (PPO) based EPMM membranes, and to characterize their physical and gas transport properties. In particular, the effects of inorganic loading and the membrane post-treatment protocol on the permeability and selectivity of the membranes were of interest. However, the results showed that the obtained permeation and separation were virtually not affected by the theoretical Si loading and the post-treatment protocol. Moreover, in comparison to the base PPO membranes, the observed O2 permeability and the O2/N2 permselectivity have generally decreased. The differential scanning calorimetry (DSC) analysis of the synthesized membranes showed an important scatter of the glass transition temperatures (Tg) of the EPMM membranes with the values generally lower than the Tg of the base PPO. Moreover, the inductively coupled plasma mass spectrometry (ICP-MS) showed the silica content in selected EPMM membranes to be far below the expected theoretical level. This, in combination with the 29Si nuclear magnetic resonance (29Si NMR) results, showed that most of the already low silica content comes from the unreacted silica source (tetraethylorthosilicate) and have led to the second phase of the project in which a modified synthesis protocol has been developed. The major differences of the modified protocol compared to the original one include the replacement of a surfactant, 1-octanol, by ethanol and using greater concentrations of the reactants. To study the effect of different parameters involved in the synthesis protocol, a Gravimetric Powder experiment, in which the inorganic polymerization is carried out in an emulsion with a pure solvent rather than a polymer solution, has been designed. The Gravimetric Powder experiments have confirmed polymerization of tetraethylorthosilicate (TEOS) in the emulsion system. Using the conditions, which resulted in the maximum production of the polymerized TEOS in the Gravimetric Powder experiments, one set of new EPMM membranes has been synthesized and characterized. The new EPMM membranes have the Tg of 228.2oC, which is distinctly greater compared to the base PPO, and contain one order of magnitude more of silica compared to the old EPMM membranes. More importantly, the 29Si NMR analysis has proven that the silica content in the new EPMM membranes originates from the reacted rather than unreacted TEOS. Interestingly, the observed conversion of TEOS in the new EPMM membranes, exceeding 20%, is greater than the largest conversion in the Gravimetric Powder experiments. The oxygen permeability in the new EPMM membrane of 33.8 Barrer is more than twice that of the base PPO membrane. Moreover, this increase in O2 permeability is associated with a modest increase in the O2/N2 permselectivity (4.75 versus 4.67).

An SiO x C y H z /mixed cellulose ester (MCE) composite membrane was fabricated by plasma deposition of hexamethyldisiloxane (HMDSO) monomer on the surface of an MCE substrate. The purpose is to apply the membrane for the oxygen enrichment of an O 2 /N 2 mixture. The variation in the fine structure of the plasma-polymerized layers (SiO x C y H z ) prepared at different plasma conditions was identified using slow-positron beams. Although the SiO x C y H z layers displayed similar FTIR spectra, they evidently showed differences based on the data from Doppler broadening energy spectroscopy (DBES) and positron annihilation lifetime spectroscopy (PALS). These data indicated distinct differences in the physical structure despite the similarities in the chemical structure of the films. The deposited layer (mixture of HMDSO species and MCE species) had more hydrocarbon group, resulting in a looser structure of the deposited layer at the initial period of plasma deposition. However, the MCE species content of the deposited layer decreased with the deposition time, and the deposited layer became denser. From PALS, the o -Ps lifetime ( τ 3 , corresponding to the free-volume size) decreased along the plasma deposition layer growth direction. These results corresponded with those obtained from XPS very well. The plasma-deposited membrane was applied for O 2 /N 2 separation. The O 2 permeability decreased and the concentration of O 2 in the permeate increased with the deposition time and as the plasma power increased.

oly-trimethyl-silyl-norbornene is an high free volume glassy polymer, whose vapor sorption levels are extremely high: this property makes it attractive for the application to gas separation membranes. Sorption and dilation experiments of n-alkane vapors were performed at 35°C using, respectively, a pressure decay apparatus and an optical device. During sorption, a wide relaxation stage was observed for both penetrants. The diffusion coefficients estimated from transient sorption show a concentration dependence which is more pronounced for the larger penetrant. The pseudo-equilibrium solubilities, calculated at the end of the relaxation stage, are very high, like for Poly-trimethyl-silyl-propyne (PTMSP). The solubility isotherms were then compared with the NELF model predictions for gas solubility in glassy polymer. The Lattice Fluid parameters were obtained from a collection of infinite dilution solubility coefficients available for different hydrocarbons: fitting these data with the NELF model, one obtains that p*= 359.82 MPa, T*= 405.98 K and rho*= 1.345 Kg/L. The model results are more than satisfactory, being in good agreement with experimental data in the whole pressure range. The polymer shows a dilation behaviour typical of the glassy state and the experimental swelling coefficients are in excellent agreement with those calculated through the NELF model.

The present paper discusses the tendency of solution-cast Hyflon® AD membranes to retain unexpectedly high amounts of solvent, the possible reasons of this phenomenon and its effect on the membrane performance. Dense membranes, prepared by solution-casting and subsequent evaporation, showed large differences in their thermal, mechanical and transport properties, depending on the residual solvent content. Complete solvent removal required heating under vacuum up to well above the glass transition temperature. Analysis of the permeability, diffusion and solubility coefficients of six permanent gases showed that plasticization by the residual solvent reduces the permselectivity and increases the permeability. Data of solution-cast membranes after complete solvent removal compare well with those of a melt-pressed sample. Experimental gas transport parameters were confronted with simulated data, obtained by the Gusev–Suter Transition-State Theory (TST) method and by molecular dynamics (MD) simulations. 1H High Resolution Magic Angle Spinning Nuclear Magnetic Resonance spectroscopic analysis of the residual solvent in the polymer matrix did not reveal a particular interaction between polymer and solvent, suggesting that the solvent retention is mainly diffusion controlled.

Asymmetric gas separation membranes were prepared by the dry-casting technique from PEEKWC, a modified amorphous glassy poly(ether ether ketone). The phase inversion process and membrane performance were correlated to the properties of the polymer and the casting solution (molar mass, polymer concentration, solution rheology and thermodynamics). It was found that a broad molar mass distribution of the polymer in the casting solution is most favourable for the formation of a highly selective membrane with a dense skin and a porous sub-layer. Thus, membranes with an effective skin thickness of less than 1 μm were obtained, exhibiting a maximum O 2 /N 2 selectivity of 7.2 and a CO 2 /CH 4 selectivity of 39, both significantly higher than in a corresponding thick dense PEEKWC membrane and also comparable to or higher than that of the most commonly used polymers for gas separation membranes. The CO 2 and O 2 permeance were up to 9.5×10 −3 and 1.8×10 −3 m 3 /(m 2 h bar) (3.5 and 0.67 GPU), respectively.