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A novel polymer of intrinsic microporosity (PIM) was prepared from a diaminobenzotriptycene monomer using a polymerization reaction based on Tröger's base formation. The polymer (PIM-BTrip-TB) demonstrated an apparent Brunauer, Emmet, and Teller (BET) surface area of 870 m2 g-1, good solubility in chloroform, excellent molecular mass, high inherent viscosity and provided robust thin films for gas permeability measurements. The polymer is highly permeable (e.g., PH2 = 9980; PO2 = 3290 Barrer) with moderate selectivity (e.g., PH2/PN2 = 11.0; PO2/PN2 = 3.6) so that its data lie over the 2008 Robeson upper bounds for the H2/N2, O2/N2, and H2/CH4 gas pairs and on the upper bound for CO2/CH4. On aging, the polymer demonstrates a drop in permeability, which is typical for ultrapermeable polymers, but with a significant increase in gas selectivities (e.g., PO2 = 1170 Barrer; PO2/PN2 = 5.4).

Room-temperature sodium–sulfur (RT Na–S) batteries have recently gained attention as next-generation energy storage devices owing to their low cost, the abundance of sodium, and the high theoretical capacity of sulfur. However, the notorious shuttle effect, caused by the dissolution of intermediate polysulfides during cycling, limits the long-term performance of Na–S batteries. In this study, intrinsically microporous Troger's base based polymer (PIM-EA-TB)-based carbon–sulfur composites are prepared for shuttle-effect-free RT Na–S batteries by utilizing the combination of physical confinement and covalent bonding in a single material. The composites demonstrate excellent electrochemical performance, including a negligible capacity fading over 350 cycles and a high coulombic efficiency of approximately greater than 99%.

Pervaporation (PV), a membrane process in which the feed is a liquid mixture and the permeate is removed as a vapour, offers an energy-efficient alternative to conventional separation processes such as distillation, and can be applied to mixtures that are difficult to separate, such as azeotropes. Here the principles of pervaporation and its industrial applications are outlined. Two classes of material that show promise for use in PV membranes are described: Polymers of intrinsic microporosity (PIMs) and 2D materials such as graphene. The literature regarding PV utilizing the prototypical PIM (PIM-1) and it hydrophilic hydrolysed form (cPIM-1) is reviewed. Self-standing PIM-1 membranes give competitive results compared to other membranes reported in the literature for the separation of alcohols and other volatile organic compounds from aqueous solution, and for organic/organic separations such as methanol/ethylene glycol and dimethyl carbonate/methanol mixtures. Blends of cPIM-1 with conventional polymers improve the flux for dehydration of alcohols. The incorporation of fillers, such as functionalised graphene-like fillers, into PIM-1 to form mixed matrix membranes can enhance the separation performance. Thin film composite (TFC) membranes enable very high fluxes to be achieved when a suitable support with high surface porosity is utilised. When functionalised graphene-like fillers are introduced into the selective layer of a TFC membrane, the lateral size of the flakes needs to be carefully controlled. There is a wide range of PIMs and 2D materials yet to be explored for PV applications, which offer potential to create bespoke membranes for a wide variety of organic/aqueous and organic/organic separations.

Materials that are capable of actuation in response to a variety of external stimuli are of significant interest for applications in sensors, soft robotics, and biomedical devices. Here, we present a class of actuators using composites based on a polymer of intrinsic microporosity (PIM). By adding an activated carbon (AX21) filler to a PIM, the composite exhibits repeatable actuation upon solvent evaporation and wetting and it is possible to achieve highly controlled three-dimensional actuation. Curled composite actuators are shown to open upon exposure to a solvent and close as a result of solvent evaporation. The degree of curling and actuation is controlled by adjusting the amount of filler and evaporation rate of the solvent casting process, while the actuation speed is controlled by adjusting the type of solvent. The range of forces and actuation speed produced by the composite is demonstrated using acetone, ethanol, and dimethyl sulfoxide as the solvent. The maximum contractile stress produced upon solvent desorption in the pure PIM polymer reached 12 MPa, with an ultimate force over 20 000 times the weight of a sample. This form of the composite actuator is insensitive to humidity and water, which makes it applicable in an aqueous environment, and can survive a wide range of temperatures. These characteristics make it a promising actuator for the diverse range of operating conditions in robotic and medical applications. The mechanism of actuation is discussed, which is based on the asymmetric distribution of the carbon filler particles that leads to a bilayer structure and the individual layers expand and contract differently in response to solvent wetting and evaporation, respectively. Finally, we demonstrate the application of the actuator as a potential drug delivery vehicle, with capacity for encapsulating two kinds of drugs and reduced drug leakage in comparison to existing technologies.

The electrospinning of high-performance polyimides (PI) has recently sparked great interest. In this study, we explore the effect of the electrospinning parameters — namely polymer concentration, voltage, tip-to-collector distance and flow rate — and salt addition on the diameter, morphology, and spinnability of electrospun PI nanofibers. Three different polyimides of intrinsic microporosity (PIM-PIs) with high Brunauer–Emmett–Teller (BET) ranging from 270 to 506 m2 g−1, and two microporous polyimides, were synthesized through the polycondensation of 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and aromatic diamines. The addition of tetraethylammonium bromide (TEAB) salt considerably increased the conductivity of all the PI solutions, significantly improved spinability, and resulted in thinner fibers. We also used molecular dynamic simulations to investigate the macromolecular mechanism of improved spinnability and fiber morphology in the presence of an ammonium salt. The small droplets detached from the parent droplet, followed by the rapid evaporation of the ions through the hydration effect, which facilitated the electrospinning. The resulting uniform nanofibers have great potential in environmental applications due to the presence of microporosity and hydrophobic pendant trifluoromethyl groups, which enhance the sorption performance of the fibers for hydrophobic species.

The potential of an ultrapermeable benzotriptycene-based polymer of intrinsic microporosity (PIM-TMN-Trip) for the upgrading of biogas is investigated. Permeation experiments were performed using an in-house bespoke permeation unit for pure gases and gas mixtures, and included tests with model mixtures as well as real biogas from a sewage treatment plant, under dry and humid conditions. Permeability and CO2/CH4 selectivity for either pure gases or for real biogas were high and lie close to or on the recently defined 2019 Robeson upper bound based on ideal permselectivities. In addition, a remarkable increase in CO2/CH4 selectivity was observed after two weeks of continuous exposure to CO2 due to a significant decrease of CH4 permeability. The constant CO2 permeability and increased selectivity upon ageing suggest that ageing in the presence of CO2 causes a rearrangement, rather than a reduction of the fractional free volume. The mixed gas permeability experiments were performed with high stage-cut in order to mimic a real separation process, and the results confirmed the potential of PIM-TMN-Trip membranes for biogas upgrading.

Flue gas purification experiments were performed with a membrane made from the ultrapermeable polymer of intrinsic microporosity (PIM) based on tetramethyltetrahydronaphthalene unit coupled with bicyclic triptycene (PIM-TMN-Trip). Permeation experiments with a CO2-N2-O2-SO2 mixture, simulating flue gas from power plants, were performed by means of an in-house developed permeation unit. The results showed very high permeability of the membrane for sulfur dioxide SO2 and high permeability of CO2, lying mainly between the Robeson upper bound form 2008 and the recently reported upper bound from 2019. Moderately high mixed gas selectivity of SO2 and CO2 with respect to N2 (21–29 and 11–18, respectively), in combination with very high permeability (28·103 and 30·103 Barrer, respectively), suggest potential use for industrial gas separation processes. The SO2/CO2 mixed gas selectivity was relatively low (around 1.8), but comparable with other novel membranes, and both are removed simultaneously in the process of CO2 separation.

This manuscript describes the gas separation performance of PIM-2, a partially fluorinated linear copolymer synthesized from 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethylspirobisindane (TTSBI) and decafluorobiphenyl (DFBP). As one of the early members of the family of polymers of intrinsic microporosity, it had never been tested as a gas separation membrane because of insufficient mechanical resistance. This has been solved only recently, allowing the preparation of robust self-standing films. Molecular modelling studies demonstrated a high fractional free volume (34%) and an elevated surface area (642 m2 g-1), and the latter is in good agreement with experimental BET results. Pure gas permeabilities measured on a fixed-volume time-lag instrument at 1 bar compare well with the results of mixed separation tests on a variable volume setup from 1-6 bar(a). Molecular modelling and independent sorption measurements on a gravimetric sorption balance both show strong dual-mode sorption behaviour, especially for CO2 and to a lesser extent for CH4. Temperature-dependent pure gas permeation measurements show typical Arrhenius behaviour, with a clear increase in the activation energy for diffusion with the increasing molecular size of the gas, indicating high size-selectivity. This is in agreement with the highly rigid PIM structure, determined by AFM force spectroscopy measurements. The dual-mode behaviour results in a moderate pressure dependence of the CO2 permeability and the CO2/N2 and CO2/CH4 selectivity, all slightly decreasing with increasing pressure. The presence of humidity in the gas stream has a remarkable small effect on the membrane performance, which is probably due to the high fluorine content and the consequently low water vapour solubility in the polymer, as confirmed by gravimetric sorption measurements. The manuscript describes an extensive study on the structure-property relationships in PIM-2. © 2019 Elsevier B.V. European Commission, EC Grantová Agentura Ceské Republiky, GA Ä?R: 18-05484S --Research on biogas upgrading presented in this work was supported by EU structural funding in the frame of Operational Programme Research, Development and Education, project No. CZ.02.1.01./0.0/0.0/17_049/0008419 “COOPERATION”. This work was further supported by the CNR-CAS bilateral agreement 2016–2018 “Innovative polymeric membranes for pervaporation and advanced gas and vapour separations” and by the Czech Science Foundation (grant no. 18-05484S ). Appendix A

The relationship, during physical aging, between the transport properties and Young’s modulus for films of polymers of intrinsic microporosity (PIM) was investigated using pure gas permeability and atomic force microscopy (AFM) in force spectroscopy mode. Excellent agreement of Young’s modulus measured for the archetypal PIM-1 with values obtained by other techniques in the literature, confirms the suitability of AFM force spectroscopy for the rapid and convenient assessment of mechanical properties. Results from different polymers including PIM-1 and five ultrapermeable benzotriptycene-based PIMs provide direct evidence that size selectivity is strongly correlated to Young’s modulus. In addition, film samples of one representative PIM (PIM-DTFM-BTrip) were subjected to both normal physical aging and to accelerated aging by thermal conditioning under vacuum for comparison. Accelerated aging resulted in a similar decrease in permeability and increase in Young’s modulus as normal aging, however, significant differences suggest that thermally induced accelerated aging occurs throughout the bulk of the polymer film whereas normal aging occurs predominantly at the surface of the film. For all PIMs, the increased in film rigidity upon aging led to an increase in gas size selectivity.

High permeance membranes were produced by addition of highly permeable nanoparticulate fillers (hypercrosslinked polystyrene, HCP, and its carbonized form, C-HCP) to a high free volume polymer (polymer of intrinsic microporosity PIM-1) in a thin film (typically 2 µm) on a porous polyacrylonitrile support. Self-standing mixed matrix membranes (MMMs) of thicknesses in the range 40–90 µm were also prepared with the same polymer and fillers. While robust MMMs could only be formed for moderate filler loadings, thin film nanocomposite (TFN) membranes could be produced from dispersions with filler loadings up to 60 wt%. On increasing the filler loading, CO2 permeance increased in line with the predictions of the Maxwell model for a highly permeable filler. Physical ageing led to some loss of permeance coupled with an increase in CO2/N2 selectivity. However, for TFN membranes the greatest effects of ageing were seen within 90 days. After ageing, TFN membranes showed high permeance with reasonable selectivity; for example, with 60 wt% C-HCP, CO2 permeance > 9300 GPU, CO2/N2 selectivity ~ 11.

Physical aging of polymer of intrinsic microporosity PIM-1 is one of the major obstacles for its application as a commercial membrane material for gas separation. In this work, physical aging of PIM-1 and matrices of this same polymer containing graphene-like materials were studied. Graphene-like fillers resulted from the functionalization of graphene oxide (GO) with two alkyl chains of different lengths, using octylamine (OA) and octadecylamine (ODA), and further chemical reduction. Extents of membrane aging were evaluated through changes in gas permeability over time; the separation of gas mixtures comprising carbon dioxide and methane, which are of great interest for industrial applications such as the production of biogas or the purification of natural gas, was carried out. 50:50 vol% CO 2 /CH 4 mixtures were used as feed and separation performance analysed for fresh membranes and at intervals of approximately a month up to 155 days. At the end of this testing period, aged PIM-1 membranes showed a CO 2 permeability of (2.0 ± 0.7) × 10 3 Barrer, which corresponds to a CO 2 permeability reduction of 68% from the value obtained right after their fabrication. The addition of alkyl-functionalized GO is shown to be an efficient strategy to retard the physical aging of PIM-1 membranes; filler loadings as low as 0.05 wt% of reduced octyl-functionalized GO showed a CO 2 permeability of (3.5 ± 0.6) × 10 3 Barrer after 5 months, which is almost three quarters higher than that of pure PIM-1 membrane aged for the same time period and represents a reduction of just 39% from its initial value. Moreover, the addition of graphene-like materials to PIM-1 does not affect its mechanical properties.

A detailed analysis of the basic transport parameters of two triptycene-based polymers of intrinsic microporosity (PIMs), the ultrapermeable PIM-TMN-Trip and the more selective PIM-BTrip, as a function of temperature from 25 to 55 degrees C, is reported. For both PIMs, high permeability is based on very high diffusion and solubility coefficients. The contribution of these two factors on the overall permeability is affected by the temperature and depends on the penetrant dimensions. Energetic parameters of permeability, diffusivity, and solubility are calculated using Arrhenius-van't Hoff equations and compared with those of the archetypal PIM-1 and the ultrapermeable, but poorly selective poly(trimethylsilylpropyne). This considers, for the first time, the role of entropic and energetic selectivities in the diffusion process through highly rigid PIMs. This analysis demonstrates that how energetic selectivity dominates the gas-transport properties of the highly rigid triptycene PIMs and enhances the strong size-sieving character of these ultrapermeable polymers.

WOS: 000432587300048 Polymers of intrinsic microporosity (PIMs) are among the most promising candidates for the development of novel polymeric gas separation membranes for processes such as carbon capture and storage, natural gas treatment and biogas upgrading. As one of the approaches to optimize their performance, PIMs are functionalized by CO2-philic groups to improve the CO2 separation by the enhancement of specific noncovalent interactions. In this work, we show the preparation of amine-PIM from the archetypal PIM-1, using borane dimethyl sulphide complexes in order to control the degree of conversion. The PIM-1 to amine-PIM-1 conversion was characterized by ATR-IR and NMR analysis. The influence of the amine moiety on the gas transport behaviour was investigated by two complementary techniques: gas permeation measurements by the time lag method and analysis of the sorption kinetics and the equilibrium sorption isotherms by the gravimetric method. Both techniques show that permeability decreases with increasing degree of conversion. The trends in the indirectly calculated solubility confirm those of direct analysis, although quantitative comparison of the two shows fundamental differences. A pressure and temperature study on a fully converted sample indicates that the solution-diffusion model should be expressed in concentration dependent transport parameters to be correct. The experimental work was supported by quantum mechanics studies and by molecular dynamics simulations to confirm the selective non-covalent interaction of CO2 with the amino groups. European Union's Seventh Framework Program (FP7)European Union (EU) [608490, 228631]; Czech specific university research (MSMT) [20-SVV/2017] The work leading to these results has received funding from the European Union's Seventh Framework Program (FP7/2007-2013) under grant agreements no 608490, project M4CO2 and no 228631, project DoubleNanoMem. Financial support was also received from the Czech specific university research (MSMT No. 20-SVV/2017). The University of Manchester is grateful to the Micromeritics grant program for provision of an ASAP 2050 surface area and porosity analyser.

Membranes composed of Polymers of Intrinsic Microporosity (SBF-PIMs) have potential for commercial gas separation. Here we report a combined simulation and experimental study to investigate the effect on polymer microporosity and gas permeability by placing simple substituents such as methyl, t-butyl and fused benzo groups onto PIMs derived from the spirobifluorene (PIM-SBFs). It is shown that methyl or t-butyl substituents both cause a large increase in gas permeabilities with four methyl groups enhancing the concentration of ultramicropores (1.0 nm). Long-term ageing studies (>3.5 years) demonstrate the potential of PIM-SBFs as high-performance membrane materials for gas separations. In particular, the data for the PIM derived from tetramethyl substituted SBF reaches the proposed 2015 Robeson upper bound for O2/N2 and, hence, hold promise for the oxygen or nitrogen enrichment of air. Mixed gas permeation measurements for CO2/CH4 of the aged PIM-SBFs also demonstrate their potential for natural gas or biogas upgrading

The promise of ultrapermeable polymers, such as poly(trimethylsilylpropyne) (PTMSP), for reducing the size and increasing the efficiency of membranes for gas separations remains unfulfilled due to their poor selectivity. We report an ultrapermeable polymer of intrinsic microporosity (PIM-TMN-Trip) that is substantially more selective than PTMSP. From molecular simulations and experimental measurement we find that the inefficient packing of the two-dimensional (2D) chains of PIM-TMN-Trip generates a high concentration of both small (

The exploration and evaluation of new composites possessing both processability and enhanced hydrogen storage capacity are of significant interest for onboard hydrogen storage systems and fuel cell based electric vehicle development. Here we demonstrate the fabrication of composite membranes with sufficient mechanical properties for enhanced hydrogen storage that are based on a polymer of intrinsic microporosity (PIM-1) matrix containing nano-sized fillers: activated carbon (AX21) or metal–organic framework (MIL-101). This is one of the first comparative studies of different composite systems for hydrogen storage and, in addition, the first detailed evaluation of the diffusion kinetics of hydrogen in polymer-based nanoporous composites. The composite films were characterised by surface area and porosity analysis, hydrogen adsorption measurements, mechanical testing and gas adsorption modelling. The PIM-1/AX21 composite with 60 wt% AX21 provides enhanced hydrogen adsorption kinetics and a total hydrogen storage capacity of up to 9.35 wt% at 77 K; this is superior to the US Department of Energy hydrogen storage target. Tensile testing indicates that the ultimate stress and strain of PIM-1/AX21 are higher than those of the MIL-101 or PAF-1 containing composites, and are sufficient for use in hydrogen storage tanks. The data presented provides new insights into both the design and characterisation methods of polymer-based composite membranes. Our nanoporous polymer-based composites offer advantages over powders in terms of safety, handling and practical manufacturing, with potential for hydrogen storage applications either as means of increasing storage or decreasing operating pressures in high-pressure hydrogen storage tanks.

Robust, ion-stabilized membranes from polybenzimidazole (PBI) and its blends with polymer of intrinsic microporosity (PIM-1) were fabricated for organic solvent nanofiltration in polar aprotic solvents (PAS). Flat sheet membranes comprising of polybenzimidazole and 4–12 wt% PIM-1 were fabricated via conventional phase inversion followed by the reduction of nitrile PIM-1 to amine PIM-1. Stabilization of the membranes were achieved via ion formation (chloride salt) under acidic condition. Such simple ion-stabilization methodology could replace cumbersome crosslinking. The aging of the membranes and the their performance at room and elevated temperatures, in a wide range of pH, in the presence of organic bases, in 6 conventional and 2 green PAS, were investigated. The PIM-1 content enabled fine-tuning of the molecular weight cut-off (MWCO) of the membranes between 190 and 650 g mol-1.

Polymers of intrinsic microporosity (PIMs) have promising gas adsorption properties for potential applications such as incorporation into high-pressure hydrogen storage tanks in an effort to increase the storage capacity or decrease the operating pressure. Such applications require detailed mechanical characterisation and determination of the structure-properties relationships to enable optimisation of the interface between the polymer and the tank. In this study, we show that Atomic Force Microscopy (AFM) nanoindentation can be used to determine the elastic modulus of cast PIM-1 films and that this property is depth-dependent. Average values of elastic modulus obtained experimentally were 1.87 GPa and are compared with elastic tensile modulus and storage tensile modulus obtained in previous studies. In addition, Scanning Electron Microscopy (SEM) and AFM imaging was performed to investigate the surface structure of the cast PIM-1 film, which has been shown to be highly granular. Polymers of intrinsic microporosity (PIMs) have promising gas adsorption properties for potential applications such as incorporation into high-pressure hydrogen storage tanks in an effort to increase the storage capacity or decrease the operating pressure. Such applications require detailed mechanical characterisation and determination of the structure-properties relationships to enable optimisation of the interface between the polymer and the tank. In this study, we show that Atomic Force Microscopy (AFM) nanoindentation can be used to determine the elastic modulus of cast PIM-1 films and that this property is depth-dependent. Average values of elastic modulus obtained experimentally were 1.87 GPa and are compared with elastic tensile modulus and storage tensile modulus obtained in previous studies. In addition, Scanning Electron Microscopy (SEM) and AFM imaging was performed to investigate the surface structure of the cast PIM-1 film, which has been shown to be highly granular.

Metal-organic frameworks (MOFs) were supported on polymer membrane substrates for the fabrication of composite polymer membranes based on unmodified and modified polymer of intrinsic microporosity (PIM-1). Layers of two different MOFs, zeolitic imidazolate framework-8 (ZIF-8) and Copper benzene tricarboxylate ((HKUST-1), were grown onto neat PIM-1, amide surface-modified PIM-1 and hexamethylenediamine (HMDA) -modified PIM-1. The surface-grown crystalline MOFs were characterized by a combination of several techniques, including powder X-ray diffraction, infrared spectroscopy and scanning electron microscopy to investigate the film morphology on the neat and modified PIM-1 membranes. The pure gas permeabilities of He, H2, O2, N2, CH4, CO2 were studied to understand the effect of the surface modification on the basic transport properties and evaluate the potential use of these membranes for industrially relevant gas separations. The pure gas transport was discussed in terms of permeability and selectivity, highlighting the effect of the MOF growth on the diffusion coefficients of the gas in the new composite polymer membranes. The results confirm that the growth of MOFs on polymer membranes can enhance the selectivity of the appropriately functionalized PIM-1, without a dramatic decrease of the permeability.

The synthesis and characterization of a series of novel hexaphenylbenzene (HPB) based polymers of intrinsic microporosity (PIM-HPBs) containing methyl, bromine, and nitrile substituents are reported. The successful formation of thin films from these polymers allowed the evaluation of the influence of the substituents on intrinsic microporosity and gas permeability. Analysis by the time-lag method also yielded information about gas diffusion coefficients and, indirectly, the gas solubility. The gas permeability varies as a function of the polarity of the substituents and shows a significant increase after treatment of the samples with methanol, especially for films cast from THF as the solvent. This enhancement, which is mostly due to an increase in the diffusion coefficient, is only partially lost upon aging of the membranes for 5 months. Measurements at different feed pressures confirm the typical dual mode sorption behavior, with increasing diffusivity and decreasing permeability and solubility as a function of the feed pressure.

A study integrating advanced experimental and modeling tools was undertaken to characterize the microstructural and interfacial properties of mixed matrix membranes (MMMs) composed of the zeolitic imidazolate framework ZIF-8 nanoparticles (NPs) and two polymers of intrinsic microporosity (PIM-1 and PIM-EA-TB). Analysis probed both the initial ZIF-8/PIM-1 colloidal suspensions and the final hybrid membranes. By combination of dynamic light scattering (DLS) and transmission electron microscopy (TEM) analytical and imaging techniques with small-angle X-ray scattering (SAXS), the colloidal suspensions were shown to consist mainly of two distinct kinds of particles, namely, polymer aggregates of about 200 nm in diameter and densely packed ZIF-8-NP aggregates of a few 100 nm in diameter with a 3 nm thick polymer top-layer. Such aggregates are likely to impart the granular texture of ZIF-8/PIMs MMMs as shown by SEM-XEDS analysis. At the molecular scale, modeling studies showed that the surface coverage of ZIF-8 NPs by both polymers appears not to be optimal with the presence of microvoids at the interfaces that indicates only a moderate compatibility between the polymer and ZIF-8. This study shows that the microstructure of MMMs results from a complex interplay between the ZIF-8/PIM compatibility, solvent, surface chemistry of the ZIF-8 NPs, and the physicochemical properties of the polymers such as molecular structure and rigidity.

The effect on the gas transport properties of Matrimid&reg, 5218 of blending with the polymer of intrinsic microporosity PIM-EA(H2)-TB was studied by pure and mixed gas permeation measurements. Membranes of the two neat polymers and their 50/50 wt % blend were prepared by solution casting from a dilute solution in dichloromethane. The pure gas permeability and diffusion coefficients of H2, He, O2, N2, CO2 and CH4 were determined by the time lag method in a traditional fixed volume gas permeation setup. Mixed gas permeability measurements with a 35/65 vol % CO2/CH4 mixture and a 15/85 vol % CO2/N2 mixture were performed on a novel variable volume setup with on-line mass spectrometric analysis of the permeate composition, with the unique feature that it is also able to determine the mixed gas diffusion coefficients. It was found that the permeability of Matrimid increased approximately 20-fold with the addition of 50 wt % PIM-EA(H2)-TB. Mixed gas permeation measurements showed a slightly stronger pressure dependence for selectivity of separation of the CO2/CH4 mixture as compared to the CO2/N2 mixture, particularly for both the blended membrane and the pure PIM. The mixed gas selectivity was slightly higher than for pure gases, and although N2 and CH4 diffusion coefficients strongly increase in the presence of CO2, their solubility is dramatically reduced as a result of competitive sorption. A full analysis is provided of the difference between the pure and mixed gas transport parameters of PIM-EA(H2)-TB, Matrimid&reg, 5218 and their 50:50 wt % blend, including unique mixed gas diffusion coefficients.

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.

High free-volume copolymers were prepared via polycondensation with 2,3,5,6,-tetrafluoroterephthalonitrile (TFTPN) in which a portion of the 3,3,3\',3\'-tetramethyl-1,1\'-spirobisindane (TTSBI) of PIM-1 was replaced with dibutyl anthracene maleimide (4bIII). An investigation of free volume using positron annihilation lifetime spectroscopy (PALS), and gas permeation measurements was carried out for the thin film composite copolymer membranes and compared to PIM-1. The average free volume hole size and the gas permeance of the copolymer membranes increased with decreasing TTSBI content in the copolymer.

No abstract

One of the challenges in the field of membrane science is to develop new materials with the proper combination of permeability and sufficiently high selectivity. For large volume applications such as natural gas treatment or CO2 sequestration from flue gas, polymers with a very high permeability in combination for an acceptable selectivity are required. A limitation of pure polymeric materials is that there is generally a trade-off between the permeability and the selectivity of the membrane and in a double logarithmic plot of selectivity versus permeability the maximum performance is limited by the so-called Robeson upper bound [1]. One of the polymers which currently performs on the this upper bound for a number of interesting gas pairs is the polymer with intrinsic microporosity PIM 1 [2] (Figure 1). Figure 1. Structure of PIM-1 [2] Mixed matrix membranes (MMMs) based on open porous nanofillers, dispersed in a dense polymer matrix, have the potential to overcome this upper bound by the synergistic action of the highly permeable porous filler and the selective dense polymeric matrix. The concept of the European project DoubleNanoMem is to embed porous nanofillers of different kind in polymers with an already high free volume and consequently high permeability, such as PIM-1. The aim of this project is to overcome the Robeson upper bound in a region where permeability is already high. In this work we present the gas permeation properties of PIM-1 based membranes with various metalorganic framework structures, dispersed in the polymer matrix. Three examples of structures used are given in Fig. 2. The transport properties of the PIM-1 based MMMs containing the given nanofillers will be discussed in detail. The three fundamental transport parameters (permeability, diffusivity and - indirectly - solubility), determined by gas permeability measurements, using a fixed volume pressure increase setup in the time lag mode will give insight into structure property relationships of porous fillers in high free volume polymers. Figure 2.Illustration of the framework structures of ZIF-8 (left), HKUST-1 (middle) and MIL-101 (right). It was found that in particular nanoZIF-8 and MIL-101 significantly enhance the performance of the MMM compared to the neat PIM-1, reaching values for CO2/N2 separation well above the Robeson upper bound (Figure 3). The discussion of the results will further focus on the difference between pure gas and mixed gas permeation, on the difference between a fixed volume pressure increase setup and a constant pressure variable volume setup with mass spectrometric analysis, on the effect of feed pressure and other experimental variables. Figure 3. Robeson diagram for the CO2/N2 pair for neat PIM-1 and representative PIM 1 MMMs, containing the nanofillers shown in Fig. 2. Solid symbols represent the as prepared membrane and open symbols represent the ethanol-treated membranes. The solid line is Robeson's 2008 upper bound [1]. Acknowledgements We are grateful to support from the Engineering and Physical Sciences Research Council (EPSRC) for AFB (Doctoral Training Account) and LMA (Materials World Network grant EP/G065144/1). The work leading to these results has further received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° NMP3-SL-2009-228631, project DoubleNanoMem. References 1.Robeson, L.M., The Upper Bound revisited, J. Membr. Sci., 2008, 320, 390. 2.P.M. Budd, N.B. McKeown, B.S. Ghanem, K.J. Msayib, D. Fritsch, L. Starannikova, N. Belov, O. Sanfirova, Y.P. Yampol'skii, V. Shantarovich, , J. Membr. Sci. 2008, 235, 851-860.

In this work, we show that the latter interpretation can efficiently represent the solubility of several gases and vapors in such polymer. Indeed, the Non Equilibrium Thermodynamic model for Glassy Polymer (NET-GP), which assumes that the polymeric phase is a dense and homogeneous one, can be applied successfully to evaluate the solubility in PIM-1 at room temperature.

The present work reports on the gas transport behavior of mixed matrix membranes (MMM) which were prepared from multi-walled carbon nanotubes (MWCNTs) and dispersed within polymers of intrinsic microporosity (PIM-1) matrix. The MWCNTs were chemically functionalized with poly(ethylene glycol) (PEG) for a better dispersion in the polymer matrix. MMM-incorporating functionalized MWCNTs (f-MWCNTs) were fabricated by dip-coating method using microporous polyacrylonitrile membrane as a support and were characterized for gas separation performance. Gas permeation measurements show that MMM incorporated with pristine or functionalized MWCNTs exhibited improved gas separation performance compared to pure PIM-1. The f-MWCNTs MMM show better performance in terms of permeance and selectivity in comparison to pristine MWCNTs. The gas permeances of the derived MMM are increased to approximately 50% without sacrificing the selectivity at 2 wt.% of f-MWCNTs' loading. The PEG groups on the MWCNTs have strong interaction with CO2 which increases the solubility of polar gas and limit the solubility of nonpolar gas, which is advantageous for CO2/N2 selectivity. The addition of f-MWCNTs inside the polymer matrix also improved the long-term gas transport stability of MMM in comparison with PIM-1. The high permeance, selectivity, and long term stability of the fabricated MMM suggest that the reported approach can be utilized in practical gas separation technology.

In the last decade PIMs have been recognized as potential candidates for the development of highly permeable and selective gas separation membranes. The archetypal PIM-1 [1], owes its microporosity and high gas permeability to a rigid contorted backbone structure [2] with dibenzodioxan and spirobisindane units. Meanwhile, functional groups like thioamide [3] and carboxylic acid [4] have been introduced into the PIM-1 structure to tailor permeability and/or selectivity for specific needs. Various other structures have been reported based for instance on polyimide backbone chemistry (PIM-PI [5]). In the present paper we will discuss the work on novel PIMs synthesized by Tröger's base formation (TB-PIM, Fig. 1). Figure 1. The structure of ethanoanthracene based TB-PIM. The rigid contorted backbone structure of these polymers of intrinsic microporosity, prevents efficient chain packing and brings them, even more than traditional glassy polymers, into a thermodynamic non-equilibrium state. One of the common features for nearly all such high free volume polymers is that there is usually a strong spread in the transport properties between different samples of one and the same polymer type. This is because their properties depend on the sample history. Sample history can be made more uniform by alcohol soaking of the PIMs, thus removing residual solvent and increasing microporosity [1]. A side-effect is that the transport properties may become strongly time-dependent after this treatment. Another complication is that these polymers seem to be also rather sensitive to the specific technique used for the gas permeation measurements and for the measurement protocol. This is the reason why many different results can be found in the literature. In this paper we will discuss in detail the transport properties of TB-PIM, and other novel members of the PIM family. In particular we will focus on the difference between pure gas and mixed gas permeation, on the difference between a fixed volume pressure increase setup and a constant pressure variable volume setup with mass spectrometric analysis, on the effect of feed pressure and other experimental variables. The basic transport parameters, permeability, diffusivity and solubility will be determined by time lag analysis and compared to those of direct sorption analysis. Finally, experimental data will be also confronted with results from structural and molecular dynamics simulation studies. Acknowledgements The work leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° NMP3-SL-2009-228631, project DoubleNanoMem. References 1.P.M. Budd, N.B. McKeown, B.S. Ghanem, K.J. Msayib, D. Fritsch, L. Starannikova, N. Belov, O. Sanfirova, Y.P. Yampol'skii, V. Shantarovich, Gas permeation parameters and other physicochemical properties of a polymer of intrinsic microporosity: Polybenzodioxane PIM-1, J. Membr. Sci. 2008, 235, 851-860. 2.N.B. McKeown and P.M. Budd, Exploitation of intrinsic microporosity in polymer-based materials, Macromolecules 2010, 43, 5163-5176. 3.C.R. Mason, L. Maynard-Atem, N.M. Al-Harbi, P.M. Budd, P. Bernardo, F. Bazzarelli G. Clarizia, J.C. Jansen, Polymer of Intrinsic Microporosity Incorporating Thioamide Functionality: Preparation and Gas Transport Properties, Macromolecules, 2011, 44, 6471-6479. 4.Du, N.; Robertson, G. P.; Song, J.; Pinnau, I.; Guiver, M. D., High-performance carboxylated polymers of intrinsic microporosity (PIMs) with tunable gas transport properties, Macromolecules 2009, 42, 6038-6043. 5.Ghanem, B.S., McKeown, N.B., Budd, P.M., Al-Harbi, N.M., Fritsch, D., Heinrich, K., Starannikova, L., Tokarev, A., Yampolskii, Y., Synthesis, characterization, and gas permeation properties of a novel group of polymers with intrinsic microporosity: PIM-polyimides, Macromolecules, 2009, 42, 7881-7888.

This work explores the use of a polymer of intrinsic microporosity (PIM-1) as the active layer within a laser sensor to detect nitroaromatic-based explosive vapors. We show successful detection of dinitrobenzene (DNB) by monitoring the real-time photoluminescence. We also show that PIM-1 has an inherent memory, so that it accumulates the analyte during exposure. In addition, the optical gain and refractive index of the polymer were studied by amplified spontaneous emission and variable-angle ellipsometry, respectively. A second-order distributed feedback PIM-1 laser sensor was fabricated and found to show an increase in laser threshold of 2.5 times and a reduction of the laser slope efficiency by 4.4 times after a 5-min exposure to the DNB vapor. For pumping at 2 times threshold, the lasing action was stopped within 30 s indicating that PIM-1 has a very fast responsivity and as such has a potential sensing ability for ultra-low-concentration explosives. Publisher PDF