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Abstract Amine absorption processes designed to remove acid gases from gas streams generally face a major challenge of solvent degradation. This degradation leads to the formation of heat-stable salts (HSS), corrosive agents that irreversibly bind free alkanolamine. The present study proposes, for the first time, a method for HSS perstraction using a liquid–liquid membrane contactor that allows HSS to transfer through porous membranes from the solvent into a hydrophobic extractant represented by a methyltrioctylammonium solution in 1-octanol. The perstraction provides selective extraction of HSS anions without direct mixing of liquid phases or the formation of stable emulsions of the solvent and the extractant. For this purpose, a number of industrial and laboratory porous membrane samples fabricated from polyvinylidene fluoride, polypropylene, and polysulfone were investigated. Their chemical and morphological stability, surface properties, and transport properties were tested under prolonged (>600 h) contact with a model solvent (an aqueous monoethanolamine solution) and with the components of the selective extractant. The feasibility of HSS perstraction was demonstrated using the formic acid (as an HSS model) extraction from the model solvent. The most promising results were obtained for a system with a polyvinylidene fluoride membrane: up to 50% of formic acid was extracted over 18 h.

The effect of ultraviolet (UV) irradiation on gas permeability and mechanical properties of low-density polyethylene (LDPE) films was investigated in the temperature range from 20°C to 60°C. It was...

Two methods for monitoring the physical aging of polymer membranes by gas permeability measurements are compared. The traditional method with intermittent permeability monitoring is compared to the continuous permeability monitoring when the membrane occurs under excess pressure of the permeating gas throughout the experiment. A composite membrane with a thin (1 μm) selective polytrimethylsilylpropyne layer containing 10 wt % organic nanoparticles (porous aromatic frameworks) was taken as an example. The continuous permeability monitoring allows acceleration of the physical aging of the membrane and considerable (by two orders of magnitude) reduction of the experiment time. Fast physical aging in a carbon dioxide stream can be an efficient way to reach equilibrium gas permeability of membranes based on glassy polymers with high void volume.

The effect of the type and amount of crosslinking reagent on the gas transport properties of polyoctylmethylsiloxane (POMS) membranes is studied for the first time. 1,7-Octadiene (OD), divinyltetramethyldisiloxane (DMDS), and two samples of polydimethylsiloxane (PDMS 500, PDMS 25000 with the molecular weights of 500, 25 000 g/mol, respectively) are used as crosslinking reagents. The permeability, diffusion, and solubility coefficients are measured for n-butane, methane, carbon dioxide, and nitrogen, and the corresponding ideal selectivities of permeability, diffusion, and solubility are calculated. It is shown that the optimal membrane properties of POMS with the use of DMDS as the crosslinking reagent are achieved at a concentration of DMDS of 3%: the maximum values of the permeability coefficient of n-butane (9400 Barrer) and ideal selectivity of permeability of n-butane/methane (26.1). A decrease in both the selectivity of solubility and selectivity of diffusion is observed for the n-butane/methane gas pair in the DMDS, PDMS 500, and PDMS 25000 series of crosslinking reagents with an increase in the fraction of a siloxane crosslinking reagent.

Composite membranes were prepared for nanofiltration of aromatic solvents. Cross-linking with AlCl3 was used to improve the stability of the PIM-1 selective layer in aromatic solvents like toluene, benzene and xylene. Nanofiltration performances of obtained membranes were tested with 4 different aromatic hydrocarbons and with 3 solvents from other classes of solvents. Obtained permeability for aromatic hydrocarbons was above 8,5 kg/m2·h·bar and retention of Remazol brilliant blue R dye with molecular mass 626 was up to 96 %. It was shown that permeability results correlated with Hansen solubility parameter and distance parameter between polymer and solvent. PIM-1 has higher permeability for non-polar hydrocarbons due to higher affinity between polymer and solvent.

Samples of nanoscale nano-PAF-10 and nano-PAF-24 porous aromatic framework-like polymeric materials were synthesized using the Suzuki reaction in a microemulsion. Monomers were tetrakis-(p-bromophenyl)methane and 1,4-phenylenediboronic acid. The main idea of the approach is to use 1,4-phenylenediboronic acid not only as a direct participant in the reaction, but also as a surfactant, which allows to stabilize the drops of the emulsion. Using this procedure, samples of PAF-like polymers were synthesized from the mixture, containing the mixture of tetrakis(p-bromophenyl)methane and 1,4-phenylenediboronic acid in ratio from 1:2 to 1:6; the reaction was conducted from 10 to 24 hours. The resulting materials were characterized by IR spectroscopy, NMR spectroscop. To estimate the particle size of the obtained materials, transmission electron microscopy was used. The object of the study were polymers, that were synthesized in 10-hour and 24-hour reactions. The particle size in the first material was in the range of 3-10 nm, in the second - from 30 to 100 nm.

Microfiltration membranes have been obtained from polymethylpentene by phase separation of its dioctyl sebacate solutions under cooling. The dissolution of the polymer was carried out at its melting point followed by formation of membrane precursors in the form of films from the resulting solution, which were then cooled and washed with acetone to remove the ester and pore formation. Using laser interferometry, it is shown that the phase diagram of the polymethylpentene–dioctyl sebacate system corresponds to amorphous separation with the UCST. The rheology of solutions is studied by rotational rheometry, and it found that the logarithm of viscosity decreases linearly with increasing concentration of dioctyl sebacate. According to calorimetry, dioctyl sebacate plasticizes polymethylpentene, reducing its crystallinity. Treatment of the resulting films with acetone leads to the complete extraction of dioctyl sebacate, and, at its concentration of 25–45 wt %, a through porous structure is formed. This procedure makes it possible to obtain fairly strong membranes with a water permeability of 16.4 kg/(m2 h atm) and a retention coefficient of submicron particles with a diameter of 240 nm equal to 80%.

The influence of casting centrifugation process parameters, such as a rotation speed (ω), the amount of the film-forming solution (V), and its concentration (C) on transport properties of composite membranes were investigated. A number of composite membranes based on poly (1-trimethylsilylpropyne) (PTMSP) and micro- (MFFK-1) and ultrafiltration (UFFK) membranes were obtained using the spin-coating method. For the first time, an unexpected dependence of permeance and ideal selectivity on rotation speed had been discovered: the thickness of the selective layer decreases from 3.0 to 1.0 μm for MFFK-1 and from 1.7 to 1.1 μm for UFFK with an increase of spin coater rotation speed from 500 to 3000 rpm. However, the gas permeance of composite membranes in the range of 500–2000 rpm was reduced due to an increase of a penetration depth of PTMSP into a support layer porous structure (estimated by the EDX method). The permeance of the PTMSP/UFFK membranes was higher than PTMSP/MFFK-1 membranes due to a thinner selective layer and a lower penetration depth of polymer solution into the pores of the support. The highest CO2/N2 selectivity values were achieved as 5.65 ± 0.9 at CO2 permeance 5600 ± 1000 GPU for PTMSP/UFFK membranes (CPTMSP = 0.35%, Vsolution = 1 mL, ω = 1000 rpm), and 6.1 ± 0.5 at CO2 permeance 4090 ± 500 GPU for PTMSP/MFFK-1 membranes (CPTMSP = 0.35%, Vsolution = 1 mL, ω = 2000 rpm).

The effect of particles of porous aromatic frameworks, synthesized by the Friedel–Crafts reaction (PAF-FC), introduced into matrix of glassy polymer poly(1-trimethylsilyl-1-propine) (PTMSP), on the stabilization of the transport characteristics of composite membranes with a thin selective layer (2.0–2.2 Μm) was studied. As a comparison, samples of composite membranes with a selective layer based on PTMSP and PTMSP filled with PAF-11 particles synthesized by the Suzuki reaction are considered. All samples of composite membranes showed a decrease in the absolute values of gas permeability for all gases over time due to relaxation of the nonequilibrium free volume of PTMSP, therewith the greatest decrease is observed during the first thousand hours since membrane creation. The stabilization of the transport characteristics of composite membranes with PTMSP/PAF-FC occurs after 5000 h since membrane creation, further the carbon dioxide performance remains at the level of 8–9 m3 m–2 h–1 atm–1 for 9200 h. Similar performance values for aged composite membranes based on PTMSP and PTMSP/PAF-11 were about 1.5 m3 m–2h–1 atm–1.

Gas transport characteristics have been studied for composite membranes with a selective layer of the highly permeable glassy polymer poly(1-trimethylsilyl-1-propyne) (PTMSP) supported on Vladipor UFFK and MFFK-1 ultrafiltration and microfiltration membranes. A modified resistance model based on the assumption of the mutual influence of the support and the selective layer on the gas transport characteristics of the composite membrane is proposed, which takes into account the penetration of PTMSP into substrate pores. A linear equation of gas transport through a composite membrane for a number of gases (N2, O2, CO2) has been obtained. It has been shown that the permeability of the supports decreases when PTMSP is applied onto them, whereas the permeability of PTMSP atop the support remains almost unchanged. The equation derived in this study can be used to analyze gas transport through composite membranes with other types of supports.

An original method of obtaining hydrophobic surfaces from blends of immiscible polymers by creating porosity through removing one of the components of the blend is considered. Polymethylpentene and polyisobutylene are used as polymers. The first polymer, which is crystallizable, is the basis for the creation of a coating, while the second polymer is amorphous and easily and completely extractable from the blend with heptane. Blends containing from 5 to 55% polyisobutylene are studied. They are characterized by the non-Newtonian behavior and low viscosity that does not reach the viscosity of the polymer matrix owing to the interlayer slip. Removing the amorphous polymer from the blend makes it possible to attain a surface porosity of 45%, which acts as a fractal surface roughness. As a result, the contact angle of polymethylpentene film with water and ethylene glycol increases from 108° to 137° and from 78° to 132°, respectively. The low viscosity of the blends provides their easy processing, including the method of 3D printing, in order to create chemically resistant hydrophobic coatings.

The porous membranes made of polyacrylonitrile (PAN) were developed by vapor induced phase separation (VIPS) technique. The effect of vapor exposure time on membrane permeability and a porous structure was investigated. All membranes exposed in water vapors have a sponge-like structure in contrast to the finger-like structure of PAN membrane obtained by non-solvent induced phase separation (NIPS) method. The obtained membranes demonstrated water permeance up to 405 kg/m2•h•bar and the retention of Blue Dextran (MW 70 kDa) on the level of 52-83%.

Previously undescribed norbornene monomer 3,3,4-trifluoro-4-perfluorohexyltricyclononene-7 is synthesized by the [2+2+2] cycloaddition reaction. The monomer is involved in the ring-opening polymerization metathesis in the presence of the first-generation Grubbs catalyst to give rise to the amorphous, glassy unsaturated polymer. The gas-transport properties of the metathesis polymer is studied, the gas permeability and diffusion coefficients for a wide range of gases (He, H2, O2, N2, CO2, CH4) are determined, and the solubility coefficients of gases in this polymer are calculated.

The influence of hyper-crosslinked polystyrene (HCPS) MacronetTM MN200 on the gas transport properties and aging of the highly permeable glassy polymer poly(1-trimethylsilyl-1-propyne) (PTMSP) was studied and analyzed in detail. The gas transport characteristics of dense PTMSP membranes containing 0–10.0 wt % HCPS were studied. It was shown that the introduction of a small amount of HCPS into the PTMSP matrix led to a 50–60% increase of the permeability coefficients of the material for light gases (N2, O2, CO2) and slowed down the deterioration of polymer transport properties over time. The lowest reduction in gas permeability coefficients (50–57%) was found for PTMSP containing HCPS 5.0 wt % after annealing at 100 °C for 300 h. It was found that HCPS sorbed residues of tantalum-based polymerization catalyst from PTMSP. In order to investigate the influence of catalysts on transport and physical properties of PTMSP, we purified the latter from the polymerization catalyst by addition of 5 wt % HCPS into polymer/chloroform solution. It was shown that sorption on HCPS allowed for almost complete removal of tantalum compounds from PTMSP. The membrane made of PTMSP purified by HCPS demonstrated more stable transport characteristics compared to the membrane made of the initial polymer. HCPS has a complex effect on the aging process of PTMSP. The introduction of HCPS into the polymer matrix not only slowed down the physical aging of PTMSP, but also reduced chemical aging due to removal of active reagents.

The mitigation of the physical aging of thin-film composite (TFC) poly[1-trimethylsilyl-1-propyne] (PTMSP) membranes was studied via the simultaneous application of a polymer-selective layer crosslinking and mixed-matrix membrane approach. For the first time, a recently developed highly porous activated carbon material (infrared (IR) pyrolyzed poly[acrylonitrile] (PAN) or IR-PAN-a) was investigated as an additive to a PTMSP-selective layer for the reduction of aging in TFC membranes. The total electric energy spent on the IR irradiation treatment of IR-PAN-a particles was twice lower than conventional heating. The flat-sheet porous microfiltration membrane MFFK-1 was used as a support, and the crosslinked PTMSP/PEI loaded with a porous filler was applied as a selective layer (0.8&ndash, 1.8 &micro, m thick) to the TFC membranes. The initial IR-PAN-a sample was additionally milled to obtain a milled IR-PAN-aM sample with a monomodal particle size distribution of 500&ndash, 800 nm. It was shown that IR-PAN-a, as a filler material with a high surface area and pore volume (2450 m2/g and 1.06 cm3/g, respectively) and a well-developed sponge-like structure, leads to the increase of the N2, O2, and CO2 permeance of PTMSP-based hybrid membrane material and the decrease of the aging of PTMSP. The simultaneous effect of crosslinking and the addition of a highly porous filler essentially improved the aging behavior of PTMSP-based TFC membranes. The monomodal and narrow particle size distribution of highly porous activated IR-pyrolyzed PAN is a key factor for the production of TFC membranes with reduced aging. The highest stability was achieved by the addition of a milled IR-PAN-aM sample (10 wt%). TFC membrane permeance was 6300 GPU (30% of initial permeance) after 11,000 h of aging at ambient laboratory conditions.

High free volume glassy polymers or polymers of intrinsic microporosity such as poly[1-trimethylsilyl-1-propyne] (PTMSP) and polybenzodioxane (PIM-1) are extra high gas permeability membrane materials. One of their major drawbacks is low gas selectivity. In this study, thin film composite (TFC) membranes have been developed with high CO2 permeance and superior CO2/N2 selectivity due to a strong synergistic effect. The TFC membranes, comprising a thin layer (0.29–0.42 μm) of PIM-1 atop a cross-linked PTMSP gutter layer (2.07–3.44 μm) on a porous backing material, were fabricated by coating PIM-1 solution on the cross-linked PTMSP support. A key element is that for coating PIM-1 a mixed solvent of chloroform and trichloroethylene (1 : 1) was successfully implemented for the first time. All membrane samples demonstrated a strong synergistic enhancement of CO2/N2 selectivity (α = 35.8–55.7) compared to PIM-1 (α = 18.5) and cross-linked PTMSP (α = 3.7). SEM, TEM and laser interferometry studies revealed that the synergistic enhancement of gas selectivity in the TFC membranes is most likely due to the creation of a very thin boundary layer between PIM-1 and the cross-linked PTMSP gutter layer. The aged TFC membranes (after three months) showed a severe drop in gas permeance while keeping nearly the same high selectivity. Thus, future success in the prevention of polymer physical aging, together with the synergy effect in selectivity reported for the first time in this work, will give new opportunities for application of polymers of intrinsic microporosity.

In this study, three different silicone rubbers with alkyl side groups were synthesized by using the recently proposed in-situ technique that combines two hydrosilylation reactions: the introduction of side alkyl group followed by polymer chains cross-linking in the same reaction mixture. The membranes can be obtained in one step by using commercially available materials such as polymethylhydrosiloxane as well as corresponded α-olefin and diolefin. The completeness of polyalkylmethylsiloxane modification was confirmed by FTIR spectroscopy. As a result, dense membranes made of polyhexylmethylsiloxane (PHexMS), polyoctylmethylsiloxane (POMS) or polydecylmethylsiloxane (PDecMS) were fabricated for further investigation of their mechanical, structural and gas transport properties. In this work membranes from PDecMS were obtained and their gas transport properties were studied for the first time. For the first time, PHexMS and PDecMS were studied for their applicability in the separation of С3+ hydrocarbons from methane. Among studied membrane materials, PDecMS demonstrates the highest selectivity for n-C4H10/CH4 gas pair separation (α = 27). An attempt was made in this work to explain from the point of view of the relationship structure-property the influence of side chain substituent in polyalkylmethylsiloxanes on gas permeabilities and selectivities of membrane materials based on them.

A method is proposed for the synthesis of new membrane materials based on polydimethylsiloxane (PDMS) and polybutadiene (PB). It has been shown that all components of the mixture completely enter into the hydrosilylation reaction and form a chemically crosslinked composite material. It has been found that in the region of low PB concentrations, the composite has a less crosslinked and dense structure. The gas transport properties of the synthesized materials have been experimentally investigated. The proposed materials have higher selectivity for organic components than the industrially used membrane polymer PDMS, which is determined by their high sorption selectivity. A membrane containing 17 wt % PB has enhanced fluxes of organic components and an increased separation factor for all alcohols (ethanol, n-propanol, and n-butanol) examined relative to those of the PDMS membrane in the pervaporative separation of water–alcohol solutions. At the same time, the ethanol–water permselectivity of such a membrane is greater than 1, a value that has been first achieved by modifying PDMS with polymers. Materials of this type have a great potential for the creation of membranes with high permeability and selectivity in the recovery of volatile organic compounds from aqueous media.

Composite membranes with a thin selective layer based on poly[1-trimethylsilyl-1-propyne] (PTMSP) and crosslinked PTMSP containing 10 wt % of nanoparticles of porous aromatic frameworks (PAF-11) have been synthesized and studied. Monitoring of changes in the gas transport characteristics of the membranes under ambient conditions for 7500 h has revealed that for all the samples, the transport characteristics abruptly decrease within the first 1000–2000 h; after that, the mass transfer constants gradually change over time. In the case of a composite membrane with the selective layer based on crosslinked PTMSP and PAF-11 nanoparticles, stable permeability values after 7000 h are 2.1, 3.5, and 12.9 m3/(m2 h atm) for N2, O2, and CO2,respectively (at an ideal selectivity of α(O2/N2) = 1.6 and α(CO2/N2) = 6.1); to date, this is the best published result for thin-film composite membranes based on highly permeable glassy polymers.

The prevention of physical aging of thin-film composite membranes based on PTMSP by the introduction of porous aromatic framework particles (PAF-11) was studied. A number of the thin-film composite (TFC) membranes with a varied thickness of the selective layer of 1.7–6.8 µm were fabricated, and its gas transport properties were monitored during up to 650 days at ambient temperature. Among all studied TFC membranes, TFC/6.8/PAF sample provided better stability of gas permeance by retaining of 0.19, 0.24 and 0.30 from its original values for N2, O2, and CO2, respectively. The best gas permeance for the stabilized aged TFC membrane were 300 (N2), 500 (O2) and 1900 GPU (CO2), and the ideal selectivity of 1.8 and 6.9 for the pair of O2/N2 and CO2/N2, respectively. It was shown that the gas selectivity of stabilized TFC membranes could be varied from 6.7 to 17 for (CO2/N2), and from 1.7 to 2.6 for (O2/N2), by adjustment of the selective layer thickness.

Silicon-substituted polynorbornenes are an unusual class of polymeric membrane materials, combining the properties of both glassy and rubbery polymers. They exhibit an attractive performance for CO2/N2 separation and for separation of gaseous hydrocarbons. However, addition polynorbornenes with Si-groups (for examples, having Si–O–C, or Si–O–Si-spacers) often suffer from poor film-forming properties due to low molecular weights of the polymers. Herein, by using a new simple and efficient approach to the synthesis of such polymers, we prepared two sets of novel high-molecular-weight polymers based on pure exo-isomers of Si-containing norbornenes and studied their gas transport properties in detail. The desired metathesis and addition polynorbornenes with (C2H5)3Si-, (CH3)3SiO(CH3)2Si- and ((CH3)3SiO)2(CH3)Si-side groups were readily obtained in good or high yields via selective hydrosilylation of norbornadiene-2,5 by commercial silanes followed by polymerization over Ru- or Pd-catalyst. Diffusion (D) and permeability (P) coefficients of these polynorbornenes were determined for permanent gases (He, H2, O2, N2, CO2) and C1–C4 alkanes. The influence of exo-/endo-orientation of substituents on gas transport properties and the relationship between nature of side-groups and membrane properties were evaluated. The data on BET, SEM, WAXD, and fractional free volumes of the polymers are also reported and discussed.

To improve the membrane permeability and separation properties in gas separation processes and thermopervaporative (TPV) recovery of butanol from model fermentation mixtures, hybrid membranes based on polymers with an extremely high free fractional volume—polytrimethylsilylpropyne (PTMSP) and hypercrosslinked polystyrene (HCL-PS)—have been first prepared and experimentally studied. The composite membranes have been fabricated using the commercial sorbent Purolite Macronet MN-200 exhibiting high sorption capacity for organic solvents. It has been found that in the hybrid membranes, HCL-PS sorbent particles are nonuniformly distributed throughout the volume: they are located in the surface layer of the membrane. It has been shown that the introduction of a small amount of a modifying component (0.5–1.0 wt %) into the PTMSP matrix improves the time stability of transport properties and increase by a factor of 1.5–2 the permeability coefficients of the material to light gases (N2, O2, CO2, CH4) and butane vapor. It has been found that hybrid PTMSP/HCL-PS membranes have higher separation factors than those of PTMSP membranes in the TPV separation of a butanol/water binary mixture.

Novel one-step technique has been proposed for octyl-substituted polymethylsiloxane (POMS) synthesis and vulcanization. The technique makes it possible to prepare С3/С1 selective gas separation membranes. The fact of POMS formation and vulcanization by hydrosilylation reaction involving 1-octene and polymethylhydrosiloxane has been confirmed by IR spectroscopy data. On the basis of the results obtained by measuring permeability of POMS membranes to permanent gases and propane, a preferred modifier to crosslinker ratio at which polymer films with the best gas transport properties can be obtained has been estimated at 95/5. Experimentally determined permeability coefficients for methane and propane (270 and 1560 barrer, respectively) and ideal propane/methane selectivity of 5.8 allow for the conclusion that POMS obtained in the study has transport properties comparable to those of similar membrane materials reported in the literature as obtained via multistep synthesis.

This work was focused on the study of physical aging of PTSMP and preventing this effect via incorporation of porous aromatic frameworks (PAF-11). The dense PTMSP membranes with PAF-11 content of 0, 1, 5 and 10 wt% were stepwise annealed in air at 100 °C for up to 510 h with constant monitoring of O 2 , N 2 and CO 2 permeability (measured at 30 °C). As-cast and aged PTMSP samples were characterized by means of helium pycnometry, dynamic mechanical analysis and IR spectroscopy. Gas transport characteristics of the PTMSP sample containing 10 wt% of PAF-11 became stable upon annealing at 100°С within the short time interval (100–200 h). However, for all other samples containing 5 wt% of PAF-11 or less, gas permeability gradually decreased with time. According to the IR analysis, upon high-temperature treatment, PAF-11 nanoparticles tended to migrate from the sub-layer region into the membrane matrix bulk. According to the helium pycnometry, the introduction of PAF-11 to the PTMSP matrix provided a loosened packaging of polymer chains, and the structure became more stabilized since the porous filler served as a “physical” cross-linker.

In the development of the composite gas separation membranes for post-combustion CO2 capture, little attention is focused on the optimization of the membrane supports, which satisfy the conditions of this technology. The primary requirements to the membrane supports are concerned with their high CO2 permeance. In this work, the membrane supports with desired characteristics were developed as high-permeance gas separation thin film composite (TFC) membranes with the thin defect-free layer from the crosslinked highly permeable polymer, poly[1-(trimethylsilyl)-1-propyne] (PTMSP). This layer is insoluble in chloroform and can be used as a gutter layer for the further deposition of the СÐ2-selective materials from the organic solvents. Crosslinking of PTMSP was performed using polyethyleneimine (PEI) and poly (ethyleneglycol) diglycidyl ether (PEGDGE) as crosslinking agents. Optimal concentrations of PEI in PTMSP and PEGDGE in methanol were selected in order to diminish the undesirable effect on the final membrane gas transport characteristics. The conditions of the kiss-coating technique for the deposition of the thin defect-free PTMSP-based layer, namely, composition of the casting solution and the speed of movement of the porous commercial microfiltration-grade support, were optimized. The procedure of post-treatment with alcohols and alcohol solutions was shown to be crucial for the improvement of gas permeance of the membranes with the crosslinked PTMSP layer having thickness ranging within 1â2.5 μm. The claimed membranes showed the following characteristics: CO2 permeance is equal to 50â54 m3(STP)/(m2 h bar) (18,500â20,000 GPU), ideal CO2/N2 selectivity is 3.6â3.7, and their selective layers are insoluble in chloroform. Thus, the developed high-permeance TFC membranes are considered as a promising supports for further modification by enhanced CO2 selective layer formation. Keywords: Thin-film composite membrane, Gas permeance, PTMSP, Crosslinking, Carbon dioxide capture

The insoluble polyimides are the most promising group of polymer materials for fabrication of solvent stable filtration membranes suitable for operation at elevated temperatures. In order to synthesize asymmetric membranes from insoluble polyimide, it is proposed to fabricate the membranes from a pre-polymer solution (polyamide acid – PAA) by non-solvent induced phase separation method followed by imidization to form non-soluble porous polyimide membrane. The thermoplastic crystallizable polyimide R-BAPB, which is resistant to a number of known organic solvents, was chosen as a membrane material. For the first time, hollow fiber membranes based on imidized PAA (R-BAPB) with a controlled distribution of pores on the inner side of the hollow fiber were formed. It has been established that the use of “hard” non-solvents, such as water or aqueous-organic solutions, is preferable for the formation of a porous structure in the membranes based on PAA (R-BAPB). Synthesized PAA membranes were used to prepare porous membranes based on the thermoplastic polyimide R-BAPB by thermal imidization. Imidization process was confirmed by an increase in the glass transition temperature of the material to 220 °C (corresponds to the glass transition temperature of polyimide (R-BAPB)) and is accompanied by a significant increase in its elastic modulus. The results of the measurements of the transport properties of polyimide membranes for gases and liquids indicate that microfiltration transport pores are present in the membranes.

Dense bilayer PTMSP/PIM-1 membranes and PTMSP/PIM-1 blends were prepared and studied in order to obtain insight into the recently observed synergistic effect of increased CO2/N2 selectivity for thin-film composite (TFC) membranes consist of PIM-1 (selective layer) and PTMSP (gutter layer). It was shown that the mixing of these two polymers does not lead to a synergistic effect in gas permeance, since dense films made by blending of PIM-1 and PTMSP showed classical trade-off permeation/selectivity behavior. Analysis of gas-transport property data using a bicomponent resistance-in-series model allowed us to conclude that the increased N2 transport resistance of the layer formed on the border of the two polymers is presumably responsible for the increased ideal selectivity.

Herein four modified polymers were prepared from readily available addition poly(5-vinyl-2-norbornene) (PVNB) and their gas-transport properties were studied in detail. Hydrogenation, epoxidation, cyclopropanation and thiol-en reactions were chosen for the modifications of PVNB. Hydrogenation of PVNB was performed using p-toluenesulfonyl hydrazide. Epoxidation of PVNB was realized employing m-chloroperoxybenzoic acid. Cyclopropanation of PVNB was carried out using diazomethane in the presence of a Pd-catalyst. For thiol-en reaction, thioacetic acid was applied as the source of a thiol and AIBN as an initiator. All listed modifications were performed in high yields (≥80%) without the destruction of polymer main chains. The degree of functionalizations was up to 99%. The influence of these modifications on the properties of the resulting polymers was evaluated. Cyclopropanation and hydrogenation of PVNB led to an enhancement of gas permeability with minimal decrease in selectivity, while epoxidation or thioacetylation gave a substantial increase in CO2/N2 selectivity with decrease in permeability. The modified polymers with polar side-groups exhibited attractive selectivities for CO2/N2, CO2/CH4 and H2/N2 gas separations.

In this study, the gas-liquid membrane contactor was considered for regeneration of the room-temperature ionic liquids (RTIL) that can be used as physical solvents for carbon dioxide capture process at elevated pressures. Poly[1-(trimethylsilyl)-1-propyne] (PTMSP) was selected as a membrane material due to its high mass transport characteristics and good mechanical properties. Nine different RTILs, such as [Emim][DCA], [Emim][BF4], [Emim][DEP], [Bmim][BF4], [Bmim][Tf2N], [Hmim][TCB], [P66614][DCA], [P66614][Br] and [P66614][Phos], were used to evaluate the solvent-membrane compatibility. The long-term sorption tests (40+ days) revealed that the solvent-membrane interaction is mainly determined by the liquid surface tension regardless of viscosity and molecular size of RTILs. For instance, [Emim][BF4] and [Emim][DCA], having the surface tension of 60.3 and 54.0 mN/m, demonstrated a very low affinity to the bulk material of PTMSP (sorption as low as 0.02 g/g; no swelling); while for the next ionic liquid [Bmim][BF4] with surface tension of 44.4 mN/m, the sorption and swelling of PTMSP was 0.79 g/g and 21%, respectively. The long-term RTIL permeation test (Δp = 40 bar, T = 50°С t > 400 h) confirmed that there is no hydrodynamic flow through PTMSP for [Emim][DCA] and [Emim][BF4]. The concept of CO2 stripping from RTIL with the membrane contactor by the pressure (Δp = 10 bar) and temperature (ΔT = 20 °С) swing was proved by using dense PTMSP membrane and [Emim][BF4]. The overall mass transfer coefficient value was equal to (1.6 − 3.8) × 10−3 cm/s with respect to liquid flow rate. By using the resistance-in-series model, it was shown that the membrane resistance contribution to the gas transfer was estimated to be approximately 8%.

Mixed matrix membranes (MMMs) with unique transport characteristics can be prepared by the addition of the minor amounts of carbon nanotubes. Changes in the membrane performance are shown to be provided by the formation of a percolation cluster composed of nanotubes. For MMMs based on poly(trimethylvinylsilane) (PVTMS) containing carbon nanotubes (CNT), due to the formation of the CNT percolation cluster, gas permeability increases by a factor of 5-15. Numerical simulation proves that the above negative changes are provided by the agglomeration of nanotubes and subsequent deterioration of the percolation structure in the membranes.

A series of microfiltration membranes were fabricated by the extraction of polyisobutylene (PIB) from its immiscible blends with polymethylpentene (PMP). Three PIB with different molecular weight of 7.5 &times, 104 (Oppanol B15), 34 &times, 104 (Oppanol B50) and 110 &times, 104 (Oppanol B100) g/mol, respectively, were used to evaluate the effect of molecular weight on the porous structure and transport properties of resulting PMP-based membranes. To mimic the conditions of 3D printing, the flat-sheet membranes were fabricated by means of melting of mixtures of various PMP and PIB concentrations through the hot rolls at 240 ∘ C followed by a quick cooling. The rheology study of individual components and blends at 240 ∘ C revealed that PIB B50 possessed the most close flow curve to the pure PMP, and their blends demonstrated the lowest viscosity comparing to the compositions made of PIB with other molecular weights (B15 or B100). SEM images of the cross-section PMP membranes after PIB extraction (PMP/PIB = 55/45) showed that the use of PIB B50 allowed obtaining the sponge-like porous structure, whereas the slit-shaped pores were found in the case of PIB B15 and PIB B100. Additionally, PMP/B50 blends demonstrated the optimum combinations of mechanical properties (str = 9.1 MPa, E = 0.20 GPa), adhesion to steel (adh = 0.8 kPa) and retention performance (R240 nm = 99%, R38 nm = 39%). The resulting membranes were non- or low-permeable for water if the concentration of PIB B50 in the initial blends was 40 wt.% or lower. The optimal filtration performance was observed in the case of PMP/B50 blends with a ratio of 55/45 (Pwater = 1.9 kg/m2hbar, R240 nm = 99%, R38 nm = 39%) and 50/50 (Pwater = 1100 kg/m2hbar, R240 nm = 91%, R38 nm = 36%).

For the development of high efficiency porous supports for composite membrane preparation, polysulfone (PSf) hollow fiber membranes (outer diameter 1.57 mm, inner diameter 1.12 mm) were modified by air plasma using the low temperature plasma treatment pilot plant which is easily scalable to industrial level and the Piranha etch (H2O2 + H2SO4). Chemical and plasma modification affected only surface layers and did not cause PSf chemical structure change. The modifications led to surface roughness decrease, which is of great importance for further thin film composite (TFC) membranes fabrication by dense selective layer coating, and also reduced water and ethylene glycol contact angle values for modified hollow fibers surface. Furthermore, the membranes surface energy increased two-fold. The Piranha mixture chemical modification did not change the membranes average pore size and gas permeance values, while air plasma treatment increased pore size 1.5-fold and also 2 order enhanced membranes surface porosity. Since membranes surface porosity increased due to air plasma treatment the modified membranes were used as efficient supports for preparation of high permeance TFC membranes by using poly[1-(trimethylsilyl)-1-propyne] as an example for selective layer fabrication.

Mixed matrix membranes (MMMs) with unique transport characteristics can be prepared by the addition of the minor amounts of carbon nanotubes. Changes in the membrane performance are shown to be provided by the formation of a percolation cluster composed of nanotubes. For MMMs based on Poly(methyl methacrylate) (PMMA) containing carbon nanotubes (CNT), due to the formation of the CNT percolation cluster, gas permeability increases by a factor of 2.5-10.

Mixed matrix membranes (MMMs) with unique transport characteristics can be prepared by the addition of the minor amounts of carbon nanotubes. Qualitative (critical, effective, marked) changes in the membrane performance are shown to be provided by the formation of a percolation cluster composed of nanotubes. For MMMs based on poly(trimethylvinylsilane) (PVTMS) containing carbon nanotubes (CNT), due to the formation of the CNT percolation cluster, gas permeability increases by a factor of 5-15. When the CNT content in the MMMs is higher than the percolation threshold, gas permeability remains on the same level or even decreases. Numerical simulation proves that the above negative changes are provided by the agglomeration of nanotubes and subsequent deterioration of the percolation structure in the membranes.