Mesoscopic simulation of an ionomeric membrane based on sulfonated aromatic poly(ether ether ketone)

Mesoscopic simulation in the framework of the mesoscopic dynamics method (a version of the dynamic density functional method) was performed for a proton conducting membrane based on sulfonated aromatic poly(ether ether ketone) in a wide range of water content in the system. For the selected parametric field, the model demonstrates microphase separation of hydrophilic and hydrophobic segments of the polymer. In the bulk of the membrane, a spatial network of water channels forms, whose walls consist of polar (sulfonated) units of the macromolecule. Independent molecular dynamics simulation for one set of parameters gives close values of the structural characteristics of the membrane, which confirms the correctness of the mesoscopic model.     

Anisotropic linear thermal expansivity of poly(ether-ether-ketone)

This paper deals with anisotropic behavior of thermal expansivity (α) of poly(ether-ether-ketone) (PEEK) sample prepared by compression molding above the melting point of polymer. The α was determined using thermo mechanical analyzer (TMA) for the temperature interval 50-250 °C in expansion mode. It is found that out-of-plane thermal expansivity (α_z) is 3.8-fold of the in-plane thermal expansivity (α_xy) below the glass transition temperature (T_g) of PEEK while α_z is decreased to 1.8-fold of the α_xy above the T_g. Moreover, the average α_z over the range studied is about 2.2-fold of the α_xy. This anisotropic behavior may be attributed to the alignment of polymer spherulites and chains along in-plane direction due to compressive forces under hot compression molding.     

Synthesis of sulfonated aromatic poly(ether amide)s and their application to proton exchange membrane fuel cells

A series of wholly aromatic sulfonated poly(ether amide)s (SPEAs) containing a sulfonic acid group on the dicarbonyl aromatic ring were prepared via a polycondensation reaction of sulfonated terephthalic acid (STA), terephthalic acid (TA), and aromatic diamine monomers. The degree of sulfonation was readily controlled by adjusting the monomer feed ratio of STA and TA in the polymerization process, and randomly sulfonated polymers with an ion exchange capacity (IEC) of 1.0–1.8 mequiv/g were prepared using this protocol. The chemical structures of randomly sulfonated polymers were characterized using NMR and FT‐IR spectroscopies. Gel permeation chromatography analysis of SPEAs indicated the formation of high‐molecular‐weight sulfonated polymer. Tough and flexible SPEA membranes were obtained from solution of N,N‐dimethylacetamide, and thermogravimetric analysis of these membranes showed a high degree of thermal stability. Compared with previously reported sulfonated aromatic polyamides, these new SPEAs showed a significantly lower water uptake of 10–30%. In proton conductivity measurements, ODA‐SPEA‐70 (IEC = 1.80 mequiv/g), which was obtained from polycondensation of 4,4′‐oxydianiline and 70 mol % STA, showed a comparable proton conductivity (105 mS/cm) to that of Nafion 117 at 80 °C. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 485–496, 2009     

Brønsted acid-base polymer electrolyte membrane based on sulfonated poly(phenylene oxide) and imidazole

The Brønsted acid-base polymer electrolyte membrane was prepared by entrapping imidazole in sulfonated poly(phenylene oxide) at the molar ratio of Im/SPPO = 2:1. The hybrid showed a high thermal stability up to 200 °C and peroxide tolerance. Differential scanning calorimetry shows that glass transition temperature is 232 °C. The conductivity increases with temperature exceeding 10⁻³ S/cm above 120 °C and a high conductivity of 6.9 × 10⁻³ S/cm was obtained at 200 °C under 33% RH conditions.     

Effect of crystalline structure on the hardness and interfacial adherence of flame sprayed poly(ether-ether-ketone) coatings

Flame sprayed PEEK (poly-ether-ether-ketone) coatings, with an amorphous structure, were subjected to isothermal treatments with annealing temperatures from 180 to 300 °C and holding times from 1 to 30 min. The coating structures were studied by means of differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses. All the annealed coatings exhibited semi-crystalline structures. Coexistence of thick and thin lamellae in the spherulites of annealed coatings can be deduced. The Knoop hardness and the interfacial adhesion of the coatings were examined. The annealed coatings exhibit higher hardness than the amorphous one. The formation of the thick lamellae is a determining factor for improving the coating hardness, which could restrict the motions and slippages of the polymer chains. However, the annealed coatings exhibit a weak adherence to the substrate. Some fissures or spherical porosities could be observed, in certain zones, on the coating/substrate interface. The formation of these fissures and porosities could be ascribed to the coating residual stress and the large volume contraction during the crystallization that occurred under the annealing conditions.     

Locally sulfonated poly(ether sulfone)s with highly sulfonated units as proton exchange membrane

Novel locally sulfonated poly(ether sulfone)s with highly sulfonated units were successfully synthesized for fuel cell applications. Poly(ether sulfone)s were prepared by the nucleophilic substitution of bis(4‐fluorophenyl) sulfone with 1,2,4,5‐tetrakis([1,1′‐biphenyl]‐2‐oxy)‐3,6‐bis(4‐hydroxyphenoxy)benzene and bis(4‐hydroxyphenyl) sulfide, followed by oxidation using m‐chloroperoxybenzoic acid. The desired highly sulfonated units were easily introduced by postsulfonation and each one had ten sulfonic acid groups. The sulfonated polymers gave tough, flexible, and transparent membranes by solvent casting. The high contrast in polarity between highly sulfonated units and hydrophobic poly(ether sulfone) units enabled the formation of defined phase‐separated structures and well‐connected proton paths. The sulfonated polymers exhibited excellent proton conductivity over a wide range of relative humidities. The proton conductivity of the sulfonated polymer with an ion exchange capacity value of 2.38 mequiv/g was comparable to that of Nafion 117 even at 30% relative humidity. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3444–3453, 2009     

Sulfonated poly(ether-ether-ketone) and Nafion composite membrane with aluminium oxide additive for fuel cell applications

The changes of physical properties and proton conductivity due to combining two polymers with inorganic compound are studied. Sulfonated poly(ether-ether-ketone) and Nafion were mixed in proportion 9 to 1; the amount of aluminium oxide nanopowder was 2 wt % counted to polymer part. Also, two-component membranes were prepared for comparison. Resulting membranes were tested for water uptake and impedance spectra were measured at low relative humidity and 70°C temperature. The highest conductivity measured in this work was obtained for ternary membrane with the value of 7.58 mS/cm.     

Aromatic and rigid rod polyelectrolytes based on sulfonated poly(benzobisthiazoles)

Aromatic polyelectrolytes based on sulfonated poly(benzobisthiazoles) (PBTs) have been synthesized by a polycondensation reaction of sulfo-containing aromatic dicarboxylic acids with 2,5-diamino-1,4-benzenedithiol dihydrochloride (DABDT) in freshly prepared polyphosphoric acid (PPA). Several sulfonated PBTs, poly[(benzo[1,2-d:4,5-d′]bisthiazole-2,6-diyl)-2-sulfo-1,4-phenylene] sodium salt (p-sulfo PBT), poly[(benzo[1,2-d:4,5-d′]bisthiazole-2,6-diyl)-5-sulfo-1,3-phenylene] sodium salt (m-sulfo PBT), their copolymers, and poly[(benzo[1,2-d:4,5-d′]bisthiazole-2,6-diyl)-4,6-disulfo-1,3-phenylene] potassium salt (m-disulfo PBT), have been targeted and the polymers obtained characterized by ¹³C-NMR, FT-IR, elemental analysis, thermal analysis, and solution viscosity measurements. Structural analyses confirm the structures of p-sulfo PBT and m-disulfo PBT, but suggest that the sulfonate is cleaved from the chain during synthesis of m-sulfo PBT. m-Disulfo PBT dissolves in water as well as strong acids, while p-sulfo PBT dissolves well in strong acids, certain solvent mixtures containing strong acids, and hot DMSO. TGA indicates that these sulfonated PBTs are thermally stable to over 500°C. Free-standing films of p-sulfo PBT, cast from dilute neutral DMSO solutions, are transparent, tough, and orange in color. Films cast from basic DMSO are also free standing, while being opaque and yellow-green. p-Sulfo PBT was incorporated as the dopant ion in polypyrrole, producing conductive films with conductivities as high as 3 S/cm and electrical anisotropies as high as 10. © 1996 John Wiley & Sons, Inc.     

Facile method for the preparation of water dispersible graphene using sulfonated poly(ether-ether-ketone) and its application as energy storage materials

A simple and effective method for the preparation of water dispersible graphene using sulfonated poly(ether-ether-ketone) (SPEEK) has been described. The SPEEK macromolecules are noncovalently adsorbed on the surface of graphene through π-π interactions. The SPEEK-modified graphene (SPG) forms an aqueous dispersion that is stable for more than six months. An analysis of the ultraviolet-visible spectra shows that the aqueous dispersion of SPG obeys Beer's law and the molar extinction coefficient has been found to be 149.03 mL mg(-1) cm(-1). Fourier transform infrared, Raman, and X-ray photoelectron spectroscopy analyses confirm successful reduction and surface modification of graphene. An atomic force microscopy (AFM) analysis reveals the formation of a single layer of functionalized graphene. Transmission electron microscopy results are also in good agreement with the AFM analysis and support the formation of single-layer graphene. SPG shows good electrochemical cyclic stability during cyclic voltammetry and charge/discharge process when used as a supercapacitor electrode. A specific capacitance of 476 F g(-1) at a current density of 6.6 A g(-1) is observed for SPG materials.     

Preparation of high performance composites based on aluminum nitride/poly(ether-ether-ketone) and their properties

Novel high performance aluminum nitride (AlN)/poly(ether-ether-ketone) (PEEK) composites containing 0-50 wt.% fractions of AlN were prepared by solution blending method followed by hot pressing to evaluate their density, melting temperature, crystallization, thermal stability, morphological behavior and Vickers hardness by using different characterization techniques. Differential scanning calorimetry results indicated that the AlN particles are very effective nucleating agent, which results in increase in melting point, hot crystallization temperature and crystallinity of composites as the AlN content increases. Thermogravimetric analysis showed enhanced thermal stability of the composites with respect to PEEK. Density and X-ray diffraction techniques showed that crystallinity of the composites increases as the wt.% of AlN content increases in polymer matrix. Scanning electron microscopy revealed that AlN particles were well dispersed with no porosity in composites. Vickers hardness of the samples increased from 24 kg/mm² for the pure PEEK to 35 kg/mm² for AlN/PEEK composites.     

Alkali metal ion conductors based on sulfonated poly(p-phenylene terephthalamide)

To obtain thermally stable and mechanically strong sodium and lithium conducting polymers, we prepared Na⁺ and Li⁺ poly(phenylene terephthalamide sulfonate salts) (MW ～ 5500). We also synthesized oligo(ethylene oxide) (3, 5, or 7 units of ethylene oxide) substituted ethylene carbonate and poly[oxymethylene-oligo(oxyethylene)]. These are high boiling point liquids with high dielectric constants as well as metal chelating properties. Polyelectrolyte systems were prepared by mixing Na⁺ or Li⁺ poly(phenylene terephthalamide sulfonate) salts with various amounts of modified ethylene carbonate and/or poly[oxymethylene-oligo(oxyethylene)]. Films (0.1–0.5 mm thick) obtained from the blends were found to have considerable mechanical strength; forming free standing films. The ionic conductivities of the Na⁺ and Li⁺ polyelectrolyte systems were 10^?6?10^?5 S/cm at 25°C. Thermal properties of these blend systems were investigated in detail. © 1994 John Wiley & Sons, Inc.     

Preparation of sulfonated poly(phthalazinone ether sulfone ketone) composite nanofiltration membrane

Thin film composite (TFC) membranes were prepared from sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) as a top layer coated onto poly(phthalazinone ether sulfone ketone) (PPESK) ultrafiltration (UF) support membranes. The effects of different preparation conditions such as the SPPESK concentration, organic additives, solvent, degree of substitution (DS) of SPPEK and curing treatment temperature and time on the membrane performance were studied. The SPPESK concentration in the coating solution was the dominant factor for the rejection and permeation flux. The TFC membranes prepared from glycerol as an organic additive show better performance then those prepared from other additives. The rejection increased and the flux decreased with increasing curing treatment temperatures. The salt rejections of the TFC nanofiltration (NF) membranes increased in the order MgCl₂ < MgSO₄ < NaCl < Na₂SO₄. TFC membranes showed high water flux at low pressure. SPPESK composite membranes rejections for a 1000 mg L⁻¹ Na₂SO₄ feed solution was 82%, and solution flux was 68 L m⁻² h⁻¹ at 0.25 MPa pressure.     

Gas permeability of cardo-poly(ether-ether-ketone) and poly(phenylene sulfide)

The gas permeability and sorption of CO₂ and N₂O was measured on cardo-poly(ether-ether-ketone) (C-PEEK) and poly(phenylene sulfide) (PPS) at 298 K. The results are discussed on the basis of the dual-mode model. Results obtained from measurements at 308 K are compared with literature data of poly(phenylene oxide) (PPO), poly(sulfone) (PSU) and poly(carbonate) (PC). While C-PEEK shows similar transport properties as PC and PSU, the values of PPS are distinctly lower. The solubility of CO₂ in the various polymers as well as the correlation of the permeability coefficients of the same polymers for He, Ar, CO₂, N₂, and CH₄ with the kinetic molecular diameter of the gases indicate a simple relation of the transport properties with the polymer density.     

Effect of heating and stretching membrane on ionic conductivity of sulfonated poly(phenylene oxide)

With chlorosulfonic acid as sulfonating agent, sulfonated poly(phenylene oxide) (SPPO) was prepared by homogeneous method and SPPO membranes were cast from its solutions in dimethylacetamide. The obtained membrane of SPPO was heat-treated and stretched with different forces by thermal mechanical analyzer under its glass transition temperature. In addition, the effects of stretching and heating on ion conductivity of SPPO were investigated by using Solatron phase analyzer. It was shown that the mechanical stretching of SPPO has great effect on electric properties of SPPO under proper heating treatment, and the highest conductivities achieved were increased about 10 times that of the original membranes and reached 0.0983 S cm⁻¹. The X-ray diffraction indicated that the molecular chains of SPPO were arranged more regularly under constraint during the heat treatment, and the scanning electron microscopy demonstrated that the morphologies of the film surfaces possessed more co-continuous regions and the hydrophilic ionic sulfonic acid groups orientated at stretching direction and connected more regularly, which facilitated the exchange and transfer of hydrated proton among these hydrophilic sulfonic acid groups.     

Structured polymer electrolyte blends based on sulfonated polyetherketoneketone (SPEKK) and a poly(ether imide) (PEI)

The performance and economics of proton-exchange membrane (PEM) fuel cells are highly dependent on the membranes used to separate the fuel and oxidant. While maintaining reasonable cost, the membrane must feature a number of desirable properties including high proton conductivity. Blends of polymers are one approach to tailoring PEM properties; however, blending to achieve mechanically and chemically robust membranes has generally resulted in reduced conductivity. The objective of this work was to demonstrate the use of field alignment of the proton-conducting domains to increase the conductivity in a polymer blend PEM. A blend of sulfonated poly(etherketoneketone) (SPEKK) and a polyether imide (PEI) was used to illustrate this method. Blends of SPEKK/PEI with a 3:7 mass ratio were aligned using electric field strengths varying from 0 to 30 V/mm and frequencies varying from 0 to 10 kHz. In general, the degree of alignment agreed with theoretical predictions for the alignment of drops or particles suspended in a fluid with a different dielectric constant, e.g., when the frequency of the applied ac field was increased, the threshold field for phase alignment increased and the diameter of the oriented columnar structures decreased. Alignment resulted in up to three orders of magnitude increase in conductivity at low humidity. By careful selection of temperature and residual solvent content, alignment was shown to be possible in the melt state, which is essential for an economic process for producing alignment-enhanced membranes.     

Properties of sulfonated poly(butylene terephthalate)

The synthesis, morphology, and mechanical properties of sulfonated poly(butylene terephthalate) (PBT) and its unsulfonated analogs were studied. The morphology of these copolymers crystallized from the melt were examined by a combination of wide-angle x-ray scattering (WAXS), polarized light microscopy, and small-angle light scattering (SALS). Stress-strain measurements are correlated with the morphological results. Spherulitic morphology, with a maltese cross at 45°C with respect to the crossed polars, is formed at low sulfonate levels (≤ 5.0 mol %). At a higher ion content, the maltese cross rotates 45° to form a cross pattern. At still higher sulfonate contents, typically 13 mol %, the light scattering pattern disappears completely. Microscopic and WAXS examination of these functionalized PBT copolymers confirms that the crystallinity level decreases with increasing ion content and is eliminated completely at the higher sulfonation level. The spherulite radius, however, remains invariant until the highest functionalization level. On the contrary, the morphology and properties of the unsulfonated isophthalate copolymer analogs remain relatively constant over the entire composition range examined. In several compositions clearly inferior properties are noted compared with the ion-containing copolymers.     

Preparation of new membranes based on sulfonated aromatic copolyimides

New sulfonated aromatic copolyimides with controlled degree of sulfonation were prepared via polycondensation reactions of a sulfonated diamine and two unsulfonated diamines with 1,4,5,8‐naphthalene tetracarboxylic dianhydride (NDA). The sulfonated diamine 3,3′‐disulfonic acid‐ bis[4‐(5‐amino‐1‐naphthoxy)phenyl]sulfone (DANPS) was synthesized through nucleophilic substitution reaction of 5‐amino‐1‐naphthol with disodium‐3,3′‐disulfonate‐4,4′‐dichlorodiphenysulfone (SDCDPS) and subsequent acidification. Two unsulfonated diamines 4,4′‐(5‐amino‐1‐naphthoxy)diphenylsulfone (ANDS) and 4,4′‐(4‐aminophenoxy)diphenylsulfone (APDS) were prepared by nucleophilic reaction of 5‐amino‐1‐naphthol and 4‐aminophenol with 4,4′‐dichlorodiphenylsulfone in the presence of potassium carbonate, respectively. After characterization of the monomers and polymers with common methods, the physical properties of the polymers including thermal behavior and stability, viscosity, molecular weight, and ion exchange capacity (IEC) were studied. The polymers showed high thermal stability and ion exchange capacity which were the basic requirements for application as fuel cell membranes. Copyright © 2008 John Wiley & Sons, Ltd.     

Adsorption of lysozyme on a hemodialysis sulfonated polyacrylonitrile membrane, with and without preadsorbed poly(ethyleneimine) on the external faces

We present the influence of pH, from pH 4 to 10, with a focus on the neutral range, on the adsorption of lysozyme (isoelectric point pI=11) on a sulphonated membrane and the same membrane pre-treated with poly(ethyleneimine) (PEI). We found a steep increase of the adsorbed amount above pH 6 in phosphate buffer. The adsorbed amount was about twice as low in Tris buffer, around the neutral pH. The difference between the two types of buffer is attributed to their different ionic composition. High interfacial concentration in phosphate buffer is especially linked to the phosphate divalent anions. In the presence of divalent sulphate anions, we measured the same level of interfacial concentration than with phosphate buffer. With the PEI pre-treated membrane, we observed, on the time scale of our experiments (15–20 h), similar adsorbed amounts than on the raw membrane, showing that the PEI layer does not constitute a true barrier to the penetration of lysozyme into the membrane core. However, its presence leads to a slower adsorption rate in a system where convection does not occur through the membrane.