Perfluorinated sulfonic acid ionomer (PFSAI) dispersions are widely used for fabrication of ion-conducting membranes and catalyst layers for hydrogen fuel cells. The conformation and concentration of PFSAIs affect the properties of the final product and depend on the liquid phase in dispersion. Here we present a novel method of preparing water/alcohol dispersions based on Nafion and Aquivion PFSAI by using a high-pressure homogenizer. The proposed route is faster and much safer and allows achieving higher PFSAI concentrations in comparison with the autoclave technique used for commercial dispersion preparation. The comparison of dispersion viscosity and PFSAI aggregate size was performed for both techniques and demonstrated similar values. Analysis of the morphology of membranes obtained from different dispersions by the casting method revealed differences in structure, which disappeared after annealing. These results highlight an important novel method of preparing PFSAI dispersions and the use of membrane morphology analysis for membrane quality evaluation.

Nanocomposite membranes based on Aquivion-type ionomer and electrospun nanofibers made from a mixture of poly(vinylidene fluoride-co-tetrafluoroethylene) (PVDF-TFE) and Aquivion-type ionomer are prepared by electrospinning and impregnation. For the first time, a short-side-chain ionomer is introduced into electrospinning mats based on PVDF-TFE and is systematically tested, including in a fuel cell. The dependence of their proton conductivity, hydrogen permeability, and morphology is determined and compared to a membrane based on pristine Aquivion-type ionomer. It is shown that nanocomposite membranes exhibit a slight decrease in proton conductivity compared to nonreinforced membranes, but improved (i.e., reduced) hydrogen gas permeability and dimensional stability. The proton conductivity of nanocomposite membranes and Aquivion-type membranes are 86 and 100 mS cm-1, respectively, at 80 degrees C and 100% relative humidity. Testing of the membrane in membrane-electrode assembly shows an increase performance compared to the original membranes and is comparable to those of the commercial Nafion 211 membrane. At a current density of 1.2 A cm-2, the composite membranes demonstrate power characteristics of 534 mW cm-2, which is comparable to the data for a commercial membrane of 571 mW cm-2. Integrating of ionomer contained nanofibers in ionomer membranes is an effective strategy of reinforcement leading to high-performance fuel cells and other ion-exchange applications.

The relationship between the mechanical, electrical, and morphological properties of annealed films based on short-side-chain perfluorinated sulfonic acid ionomer (SSCI) with an Aquivion structure was systematically investigated using dynamic mechanical analysis (DMA), small-angle X-ray scattering (SAXS), and impedance spectroscopy. Annealing the membranes at temperatures of 140, 150, and 160 degrees C-above the glass transition temperature of SSCI-and the nature of the liquid phase in the polymer dispersion significantly influence the structural parameters of the membranes, specifically the size of the conductive channels formed by hydrophilic sulfonic acid groups. SAXS and AFM analyses revealed that membranes cast from N,N-dimethylacetamide (DMAA) exhibit a denser, less structured morphology, resulting in lower hydrogen permeability (phi = 4.6 +/- 0.7 nmol/m/s/MPa), comparable to the commercial Nafion 211 membrane (phi = 6.5 nmol/m/s/MPa), but with significantly lower proton conductivity (35 +/- 5 mS/cm) than Nafion 211 (95 mS/cm). In contrast, membranes obtained from a water-alcohol mixture showed a well-defined structure (SAXS, AFM), with proton conductivity values ranging from 70 to 103 mS/cm, comparable to Nafion 211. However, the hydrogen permeability of these membranes varied significantly depending on the annealing conditions (phi = 5.5-65.3 nmol/m/s/MPa). SAXS data indicated that the membranes had a similar degree of crystallinity (11-13%) but differed in the positions of the ionomer peak and matrix knee, which are associated with variations in the size of the conductive channels and account for the observed differences in ionic conductivity. Membranes annealed at 150 degrees C, which exhibited hydrogen permeability and ionic conductivity values close to those of the commercial Nafion 211 membrane, were used to fabricate membrane electrode assemblies (MEA). The electrochemical characteristics of these MEAs were investigated at 30 and 60 degrees C, 100% relative humidity, at both atmospheric pressure and 200 kPa overpressure. At a current density of 1.75 A/cm(2), the fabricated membranes demonstrated power outputs of up to 550 and 950 mW/cm(2), which are comparable to, and even exceed, those of the commercial Nafion 211 membrane (700 mW/cm(2)). However, despite the high-power performance, significant membrane degradation was observed after 10,000 cycles in durability tests. These findings contribute to a better understanding of the relationship between the electrochemical properties and the structure of short-side-chain perfluorinated sulfonic acid ionomers with an Aquivion-type structure and are expected to enhance their application in fuel cells.

The coefficients of diffusion permeability of methanol through the synthesized polymer film–sulfonated polystyrene composite membranes and a Nafion-115 membrane are measured. For several composite membranes with significantly different transport properties, the values of the diffusion flux of methanol qdiff through these membranes under the conditions of a direct methanol fuel cell (DMFC) at 60°C and a concentration of the feed solution of 1–2 M are calculated. Direct measurements of the crossover current and methanol crossover qCVA in a DMFC based on these membranes are carried out by cyclic voltammetry (CVA). It is found that the values of qCVA are on average by 15

Ethylene-propylene-diene rubbers (EPDM) are one of the most important polyolefin materials widely commercialized and used in various industries in recent years. The production of EPDM is based solely on catalytic coordination polymerization processes. The development of new catalysts and processes for the synthesis of EPDM has expanded the range of products and their manufacturing in terms of energy efficiency, processability, and environmental safety. This mini-review mainly analyzes patented data on the synthesis of EPDM on new-generation single-site catalytic systems based on Group IVB complexes including the systems commercialized by major manufacturers of EPDM. The advantages of these systems are evident in comparison with conventional vanadium systems introduced into production in the 1960s and used to date in the industrial synthesis of EPDM.

The review analyzes and summarizes the results of investgations of lithium-conducting polymer electrolytes obtained via ion exchange from the initial H + form of perfluorinated sulfonic cation-exchange membranes of the Nafion family. Salt forms of membranes not only retain the high strength and chemical stability inherent in the parent materials, but also have increased thermal stability (compared to the protonated form). The introduction of plasticizers (dipolar aprotic solvents and their mixtures) and modifying additives makes it possible to achieve a conductivity of 10 −5 –10 −3 S/cm in the ambient temperature range. This makes polymer electrolytes based on lithiated Nafion membranes (Li-Nafion) very attractive for practical use instead of liquid nonaqueous electrolytes in electrochemical power sources. Such research is actively conducted in the field of lithium–oxygen, lithium−sulfur, and lithium-ion batteries, as well as batteries with a lithium metal negative electrode. It is proposed to use Li-Nafion not only as an electrolyte/separator, but also as a functional binder of electrode materials, as a thin barrier layer on a positive electrode or a microporous separator, as an artificial protective layer on the surface of a lithium metal electrode, etc. For all types of considered power sources, the results confirming the prospects for the development of electrochemical systems using Li-Nafion have been obtained.

Novel ion-exchange membranes based on a commercial porous polytetrafluoroethylene film and sulfonated polystyrene are synthesized. To form porous polytetrafluoroethylene–polystyrene composites, thermal polymerization of styrene sorbed in the pores of the matrix-film from the monomer solution is used. The use of porous matrix makes it possible effectively obtaining the composites, used as precursors of the ion-exchange membranes. The sulfonating of the porous polytetrafluoroethylene–polystyrene composites forms the membranes with ion-exchange capacity up to 2.8 mmol/g. The composition and ground physicochemical properties of the new proton-conducting composite membranes are investigated. The developed membranes were shown to have good transport properties. The proton conductivity of water-saturated membranes is as high as 0.13 S/cm at room temperature; the hydration number is 30. Comparative tests of the synthesized membranes and the commercial Nafion-115 membrane in a direct methanol fuel cell at 60°C showed the characteristics of the fuel cell with the developed membranes being at least not inferior to those of a Nafion-115-based cell.

The use of dipolar aprotic solvents to swell lithiated Nafion ionomer membranes simultaneously serving as electrolyte and separator is of great interest for lithium battery applications. This work attempts to gain an insight into the physicochemical nature of a Li-Nafion ionomer material whose phase-separated nanostructure has been enhanced with a binary plasticiser comprising non-volatile high-boiling ethylene carbonate (EC) and sulfolane (SL). Gravimetric studies evaluating the influence both of mixing temperature (25 to 80 °C) and plasticiser composition (EC/SL ratio) on the solvent uptake of Li-Nafion revealed a hysteresis between heating and cooling modes. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) revealed that the saturation of a Nafion membrane with such a plasticiser led to a re-organisation of its amorphous structure, with crystalline regions remaining practically unchanged. Regardless of mixing temperature, the preservation of crystallites upon swelling is critical due to ionomer crosslinking provided by crystalline regions, which ensures membrane integrity even at very high solvent uptake (≈200% at a mixing temperature of 80 °C). The physicochemical properties of a swollen membrane have much in common with those of a chemically crosslinked polymer gel. The conductivity of ≈10−4 S cm−1 demonstrated by Li-Nafion membranes saturated with EC/SL at room temperature is promising for various practical applications.

The electrotransport characteristics of the polymer electrolyte based on lithiated Nafion-115 membrane plasticized by high-boiling dipolar aprotic solvents—sulfolane (SL), ethylene carbonate (EC), and diglyme (G2) and also by their binary and ternary mixtures are studied in a wide temperature interval (from –60 to +80°C). The best transport properties (conductivity 10–5–10–4 S cm–1 in the interval from –20 to +70°C) are demonstrated by samples plasticized with binary mixtures EC/G2 and EC/SL in certain ratios. The ternary plasticizer provides low activation energy (10–20 kJ mol–1) and sufficiently high conductivity in the temperature region not lower than –10°C.

A Nafion-115 membrane in its lithiated form (Li-Nafion) was plasticised using a binary mixture of ethylene carbonate (EC) and sulfolane (SL) to obtain a polymer electrolyte with single-ion lithium conductivity and enhanced stability. The weight fraction of SL in the binary mixture varied from pure EC to pure SL with a step of 5-10 wt. %. Quantum chemical calculations at the M05-2X/TZVP + SMD theory level predicted that an EC/SL binary mixture can be a more effective plasticiser for the Li-Nafion membrane than its single components. A significant influence of mixing temperature (at which the membranes were saturated with a plasticiser) on the swelling degree of the membranes was observed; when the temperature was below the melting point of pure EC, membrane saturation was substantially less effective despite the liquid state of the binary plasticiser EC/SL. The temperature dependences of ionic conductivity of the electrolytes obey the Arrhenius law with activation energies 21 to 33 kJ mol(-1). The best sample demonstrated single-ion lithium conductivity of 6.3 x 10(-6) to 6.9 x 10(-4) S cm(-1) within the temperature range of -40 to + 80 degrees C and a negligible contribution of electronic conductivity (similar to 10(-9) S cm(-1) at 25 degrees C) together with electrochemical stability window 0 to 6 V vs. Li/Li+. Electrochemical properties of Li-Nafion swollen with the non-volatile EC/SL binary plasticiser appear to be suitable for practical applications in lithium batteries. (C) 2021 Elsevier Ltd. All rights reserved.

Quantum chemical modeling is performed for the distancing of lithium and ammonium cations from the –O–CF2–CF2–SO$$_{3}^{ - }$$ functional group typical of Nafion-like polymer membranes in the presence of a different number of dimethylsulfoxide molecules. The cluster approach plus the B3LYP density functional and 6-31G* basis are used. It is found that cations are quite strongly bound to anions in the considered systems if the number of plasticizer molecules in them is low (n ≤ 4). Solvent molecules not incorporated in the first coordination sphere can act as polarizable dielectric layers between cations and anions upon an increase in the value of n. This allows the distance between a cation and an anion to be increased to 7–14 Å with a moderate consumption of energy (∼0.3 eV).

A new approach for gas-phase modification of ultra-high-molecular-weight polyethylene (UHMWPE) film for synthesis of proton exchange membranes (PEMs) has been successfully realized. First, the membrane precursors have been prepared by soaking the films in a monomers/AIBN solution followed by their modification with polystyrene (PS) in styrene vapor at 110 degrees C. The developed method is characterized by high efficiency, simplicity, and ecological purity. The modified UHMWPE films containing up to 60 wt% of PS have been obtained. Then, PEMs were prepared by sulfonation of these precursors. According to energy-dispersive X-ray spectroscopy of the sulfonated samples, almost uniform distribution of PS through the film thickness was observed. The membranes with an ion exchange capacity up to 2.7 mmol/g and proton conductivity up to 60 mS/cm (water, 25 degrees C) were obtained. Comparative tests of the obtained UHMWPE-sulfonated PS and commercial Nafion-115 membranes in a hydrogen-air fuel cell have been carried out. It has been shown that the cell with the synthesized membranes exhibits better performance than that with Nafion-115.

The quality of ion-selective membranes determines the efficiency of Vanadium Flow Batteries (VFBs), and alternatives to expensive Nafion (TM) materials are actively being searched for. One of the membrane architecture approaches is to imitate the Nafion (TM) structure with two separate phases: a conductive sulfonated polymer and an inner matrix. We introduce a new composite material based on sulfonated styrene polymerized inside the pores of a stretched PTFE matrix. Variation of polystyrene content and a sulfonation degree allowed to obtain membranes with IEC from to 0.96 to 1.84 mmol/g. Balanced vanadium permeability (ca. 5.5 . 10(-6) cm(2)/min) and proton conductivity (ca. 50 mS/cm) were achieved for the material with 21-23 % polystyrene content and a sulfonation degree up to 94 %. Membranes showed stable cycling with 81 % energy efficiency in a single-cell VFB. This work contributes to the existing knowledge of Nafion alternatives by providing a cheap and scalable method of membrane production.

The first theoretical study of alkali-metal ion transport in a polymeric inorganic electrolyte based on a dimethyl sulfoxide-plasticized Nafion membrane is reported. The structure and intermolecular interactions in XNafion · nDMSO (X = Li, Na, K, Rb, and Cs; n = 8 and 12) ionomers are simulated by the DFT method with hybrid density functionals B3LYP, wB97XD, and PBE taking into account periodic boundary conditions and the projector augmented wave (PAW) method in the VASP and GAUSSIAN program packages. According to the calculations, the barriers rise from 0.2 to 0.4 eV in the series Li–K but lower to 0.3–0.2 eV as the radius increases further in the series Rb, Cs. These results are quantitatively consistent with experimental conductivity activation energy data: 0.26 (Li+), 0.37–0.38 (Na+, K+), 0.27 (Rb+), and 0.20 (Cs+) eV. The conclusion is drawn about the structure and conductivity of the electrolyte depending on the nature of the cations.