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► High flux in organic solvents compared to state of the art membranes. ► Retention above 99% in the nanofiltration range. ► Simple but efficient cross-linking procedure to control ...membrane properties. ► Applied membrane preparation upscalable to industrial membrane preparation.
High free volume polymers are characterized by much higher permeability and diffusivity for gases and vapors than commodity polymers. Polymers of intrinsic microporosity (PIMs), an important member of this class of polymers, are only soluble in a few solvents. This gives reason to expect stability in many solvents and an application in organic solvent nanofiltration (OSN) may be feasible. Thin film composite membranes of PIM-1 and PIM copolymers were developed on a polyacrylonitrile (PAN) porous support. For control of swelling, a simple, technically realizable method of cross-linking was produced by blending the PIM with polyethyleneimine, coating to give thin film composites (TFCs) and thermally or chemically cross-linking the separation layer on the supporting membrane. The TFCs were tested in OSN with the solvents n-heptane, toluene, chloroform, tetrahydrofuran, and alcohols, and compared to similarly cross-linked poly(trimethylsilyl propyne) TFCs and state of the art industrial Starmem™ 240 membranes. Better retention, a steeper retention curve and much higher fluxes were detected for the newly developed PIM TFC membranes.
Polymers of intrinsic microporosity (PIMs) possess molecular structures composed of fused rings with linear units linked together by a site of contortion so that the macromolecular structure is both ...rigid and highly non‐linear. For PIM‐1, which has previously demonstrated encouraging gas permeability data, the site of contortion is provided by the monomer 5,5′,6,6′‐tetrahydroxy‐3,3,3′,3′‐tetramethyl‐1,1′‐spirobisindane. Here we describe the synthesis and properties of a PIM derived from the structurally related 6,6′,7,7′‐tetrahydroxy‐4,4,4′,4′‐tetramethyl‐2,2′‐spirobischromane and copolymers prepared from combination of this monomer with other PIM‐forming biscatechol monomers, including the highly rigid monomer 9,10‐dimethyl‐9,10‐ethano‐9,10‐dihydro‐2,3,6,7‐tetrahydroxyanthracene. Generally, the polymers display good solubility in organic solvents and have high average molecular masses ($\overline {M} _{{\rm w}} $) in the range 80 000–200 000 g · mol−1 and, therefore, are able to form robust, solvent‐cast films. Gas permeability and selectivity for He, H2, N2, O2, CO2, and CH4 were measured for the polymers and compared to the values previously obtained for PIM‐1. The spirobischromane‐based polymers demonstrate enhanced selectivity for a number of gas pairs but with significantly lower values for permeability. The solubility coefficient for CO2 of two of the copolymers exceed even that of PIM‐1, which previously demonstrated the highest value for a membrane‐forming polymer. Therefore, these polymers might be useful for gas or vapor separations relying on solubility selectivity.
New polymers and copolymers of intrinsic microporosity (PIM) are synthesized to yield high molecular weight, flexible film forming polymers. Their properties, including gas permeation and separation, are analyzed. Compared to the archetype PIM‐1 lower permeabilities at higher selectivities for the gases are detected. A remarkable high solubility of CO2 for some polymers is found, which exceeds the solubility of PIM‐1 and PIM‐type polyacetylenes.
High free volume, film-forming copolymers were prepared in which a proportion of the spiro-units of PIM-1 were replaced with units derived from ...9,10-dimethyl-9,10-dihydro-9,10-ethanoanthracene-2,3,6,7-tetrol (CO1). A full investigation of free volume, utilizing N2 sorption, positron annihilation lifetime spectroscopy (PALS), Xe sorption and 129Xe NMR spectroscopy, was undertaken for copolymer PIM1-CO1-40 (spiro-units:CO1 = 60:40) and a comparison is made with PIM-1. All techniques indicate that the copolymer, like PIM-1, possesses free volume holes or pores on the nanometre length scale (i.e., microporosity as defined by IUPAC). For the batch of PIM-1 studied here, the sample as received showed anomalous N2 sorption, Xe sorption and 129Xe NMR behavior that could be interpreted in terms of reduced porosity in the size range 0.6−0.7 nm, as compared to the copolymer. The anomalous behavior was eliminated on conditioning or relaxation of the polymer, e.g., by Xe sorption at 100 °C and 3 bar. PALS for both PIM1-CO1-40 and PIM-1 indicates a maximum in the average free volume hole size, and in the width of the distribution of hole sizes, on increasing temperature. This maximum appears to be a feature of high free volume polymers and may be related to the onset of localized oscillations of backbone moieties.
Novel polymers of intrinsic microporosity (PIMs) are prepared from bis(phenazyl) monomers derived from readily available bis(catechol)s. One of the polymers (termed PIM-7) has an excellent ...combination of properties with high internal surface area, good film-forming characteristics, and gas transport properties that make it a suitable candidate for gas separation membranes. The high gas permeability and good ideal selectivity of PIM-7 place it above Robeson's upper-bound for a number of commercially important gas pairs (e.g., O2/N2, CO2/CH4, and CO2/N2).
Novel types of microporous material are required for chemoselective adsorptions, separations and heterogeneous catalysis. This concept article describes recent research directed towards the synthesis ...of polymeric materials that possess microporosity that is intrinsic to their molecular structures. These polymers (PIMs) can exhibit analogous behaviour to that of conventional microporous materials, but, in addition, may be processed into convenient forms for use as membranes. The excellent performance of these membranes for gas separation and pervaporation illustrates the unique character of PIMs and suggests immediate technological applications.
Holey polymers! The use of fused‐ring spirocyclic linking groups leads to polymers of intrinsic microporosity (PIMs; an example is illustrated here) from which adsorbents, heterogeneous catalysts and separation membranes can be derived.
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► A detailed description of a measurement principle for gas permeability under defined humidity. ► Thorough account of device setup and measurement uncertainty calculation. ► ...Significant change in the CO
2/N
2 separation performance of Pebax MH1657 at high humidity.
Many industrial gas separations in which membrane processes are feasible entail high water vapour contents, as in CO
2-separation from flue gas in carbon capture and storage (CCS), or in biogas/natural gas processing. Studying the effect of water vapour on gas permeability through polymeric membranes is essential for materials design and optimization of these membrane applications. In particular, for amine-based CO
2 selective facilitated transport membranes, water vapour is necessary for carrier-complex formation (Matsuyama et al., 1996; Deng and Hägg, 2010; Liu et al., 2008; Shishatskiy et al., 2010)
1–4. But also conventional polymeric membrane materials can vary their permeation behaviour due to water-induced swelling (Potreck, 2009)
5. Here we describe a simple approach to gas permeability measurement in the presence of water vapour, in the form of a modified constant volume/variable pressure method (pressure increase method).
We are developing new types of polymer – termed polymers of intrinsic microporosity (PIMs) – which in the solid state behave like molecular sieves. As pervaporation membranes, they show selectivity ...for organics over water. As gas separation membranes, they exhibit a remarkable combination of high permeability and good selectivity for gas pairs such as O2/N2.
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