Influence of electrolytes of Li salts,EMIMBF4, and mixed phases on electrochemical and physical properties of Nafion membrane

Electrolyte‐soaked Nafion is commonly used as an ionic polymer in soft actuators. Here, a multitechnique investigation was applied to correlate the electrochemical behavior of Nafion membranes with their microstructures and nanostructures as a function of electrolyte type. The influence of electrolytes of Li salts with different counteranions on the Nafion membranes was investigated in terms of hydration level, structure (using X‐ray diffraction and small angle X‐ray scattering), stress–strain characteristics, and electrochemical behavior (by cyclic voltammetery and electrochemical impedance spectroscopy). The effects of using ionic liquid (IL), as the electrolyte, addition of different supporting solvent and the addition of Li⁺ ions to water‐free IL‐soaked membranes on the structural and electrochemical properties of Nafion were examined. The nano‐ and microstructure of the Nafion changed considerably as a function of the identity of the electrolyte solution. The electrochemical behavior of the IL‐soaked samples was compared with that of the water‐soaked Li⁺‐exchanged Nafion. It was seen that the ionic conductivity of the Nafion membranes was reduced significantly when water was replaced by pure IL. Using the supporting solvents increased the conductivity of IL‐soaked Nafion membranes dramatically. The presence of a small amount of Li⁺ ions together with the IL ions caused a significant decrease in charge transfer resistance and increases in double layer capacitance and in ionic conductivity over that of the water‐free sample and also over water‐soaked Li⁺‐exchanged Nafion. These findings can be useful to improve the knowledge on Nafion's microstructure and also to improve the electromechanical behavior of Nafion‐based ionic polymer–metal composites actuators. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45239.     

Supercritical fluid CO2 processing and counter ion substitution of nafion® membranes

Nafion®‐117 was exposed to supercritical fluid (SCF) CO₂ and a cation solution using two different approaches: first was processed with SCF CO_2, and then exchanged using six different cations: K⁺¹, Ca⁺², Ba⁺², Cu⁺², Fe⁺³, and Al⁺³. The second method performed the cation substitution first, followed by the SCF CO₂ processing. The resulting composite membranes were characterized using several techniques: thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transforms infrared spectroscopy (FT‐IR), small angle X‐ray scattering (SAXS), and X‐ray diffraction (XRD). These techniques were used to identify the changes in the chemical and thermal properties of the membranes, as well as to evaluate changes in the resulting morphologies and crystallinities. Proton conductivity and methanol permeability were measured to understand how the different approaches promoted or inhibited the transport of certain substances through the membrane. Significant differences in their thermal, physical and transport properties were observed when Nafion® was processed with SCF CO₂ and exchanged with cations. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Phase Behavior of Glycerol Trioleate‐Based Ionic Liquid Microemulsions

Glycerol trioleate‐based ionic liquid microemulsions are promising biolubricant alternatives. This study presents the formation and the phase behavior of glycerol trioleate‐based ionic liquid microemulsions. Areas of the single‐phase domain were calculated to illustrate the phase‐forming capacities of the designed systems. The effects of ionic liquid anions and cations, oxyethylene groups’ number of surfactant, mass ratio of surfactant to co‐surfactant, chain length of co‐surfactant, and temperature on the phase behavior and phase‐forming capacities of glycerol trioleate‐based ionic liquid microemulsions were investigated using pseudo‐ternary phase diagrams. The results showed that the phase‐forming capacities of glycerol trioleate‐based ionic liquid microemulsions with different ionic liquids were Tf₂N^?‐based > PF₆^?‐based > BF₄^?‐based, OMIM⁺‐based > HMIM⁺‐based > BMIM⁺‐based > EMIM⁺‐based. The designed systems contained ionic liquid‐glycerol trioleate amphiphilic balance; thus, glycerol trioleate‐surfactant micelles achieved the maximum solubilization capacity for the ionic liquid when the surfactant had approximately five oxyethylene groups with a surfactant to co‐surfactant mass ratio of 4:1. Moreover, increasing the temperature and the aliphatic chain length of co‐surfactant from C2 to C6 enhanced the ability of glycerol trioleate and ionic liquids to form microemulsions.     

The Ionic Conductivity of a Nafion® 1100 Series of Proton‐exchange Membranes Re‐cast from Butan‐1‐ol and Propan‐2‐ol

The ionic conductivity of Nafion® 1100 extruded membranes re‐cast from solutions of butan‐1‐ol and propan‐2‐ol is measured in 0.5 mol dm^–3 H₂SO₄ at 295 K, using an immersed, four‐electrode d.c. technique. The general trend is an increasing conductivity for the thicker membranes. Materials which were solution‐cast from butan‐1‐ol yielded the highest conductivity while a series of membranes with lower conductivities (similar to those of an extruded Nafion® 1100 series of membranes) was found using propan‐2‐ol. The conductivity results indicate that membranes manufactured by extrusion and casting from various solvents might have different structures. Differences in the water content and conductivity of the membranes are considered to arise from the impact of processing conditions on the surface and bulk structure of the membranes.     

Transport properties of sulfonated poly (styrene‐isobutylene‐styrene) membranes with counter‐ion substitution

In this study, the transport properties of poly(styrene‐isobutylene‐styrene) (SIBS) were determined as a function of sulfonation level (0–94.9%) and counter‐ion substitution (Ba⁺², Ca⁺², Mg⁺², Mn⁺², Cu⁺², K⁺¹) for fuel cell applications. Increasing the sulfonation level improved the ion exchange capacity (IEC) of the membranes up a maximum (1.71 mequiv/g), suggesting a complex three‐dimensional network at high sulfonation levels. Results show that proton conductivity increases with IEC and is very sensitive to hydration levels. Methanol permeability, although also sensitive to IEC, shows a different behavior than proton conductivity, suggesting fundamental differences in their transport mechanism. The incorporation of counter‐ion substitution decreases both methanol and proton transport. Methanol permeability seems to be related to the size of the counter‐ion studied, while proton conductivity is more sensitive to water content, which is also reduced upon the incorporation of counter‐ions. To complement the studies, selectivity (i.e., proton conductivity/methanol permeability) of the studied membranes was determined and compared to Nafion® 117. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Stereoselective Behavior of Nafion® Membranes towards (+)‐α‐Pinene and (−)‐α‐Pinene

α‐Pinene enantiomers were sorbed in Nafion® membranes. The membranes included a commercial extruded Nafion® 115 membrane as well as membranes prepared by casting a Nafion® solution, evaporating the solvent, and a thermal treatment at different temperatures. The microstructure of membranes was studied by small‐angle and wide‐angle X‐ray scattering, and magic‐angle spinning nuclear magnetic resonance spectroscopy. The change of membrane weight during the sorption process was determined with a sorption microbalance. Noticeable differences concerning the sorption behavior of the various membranes could be stated. The sorption of (+)‐α‐pinene and (?)‐α‐pinene in an extruded Nafion® membrane turned out to be rather low.     

Nafion®/(SiO2, ORMOSIL,and dimethylsiloxane) hybrids via in situ sol–gel reactions: Characterization of fundamental properties

Nafion®/SiO₂, Nafion®/[ OR ganically MO dified SIL icate (ORMOSIL)] and Nafion®/dimethylsiloxane hybrids were created via in situ sol–gel reactions for tetraethoxysilane, diethoxydimethylsilane, and their mixtures. Differential scanning calorimetry studies showed a broad endotherm for unfilled Nafion®-H⁺ at T_α ≈ 215°C that shifts upward for the Q : D = 1 : 0 (mol : mol) [Q = Si(O_1/2)₄, D = (O_1/2)₂Si(CH₃)₂] hybrid, then shifts downward with decreasing Q : D. This endotherm likely arises from release of H₂O molecules bound to ≡Si—OH groups and condensation reactions among silanol groups. The decrease in T_α is rationalized in terms of an increasing fraction of flexible D units that disrupt hydrophilic Q structures. T_m shifts to lower temperatures with decreasing Q : D, and it is suggested that main chains are restricted by side chains embedded in silicon oxide nanoparticles, but D unit insertion causes side chains to be anchored less strongly. Thermal gravimetric analysis indicates that the first mass loss step for Nafion®-H⁺ shifts to higher temperatures as D : Q increases; an increase in D unit fraction inhibits Q unit degradation by evolved HF. A dynamic mechanical transition at T_α may arise from side chain motions, and the increase in T_α in passing from unfilled Nafio®-H⁺ to the 1 : 0 hybrid is due to side chain immobilization by their entrapment in silicon oxide domains. The progression 0 : 1 → 1 : 2 → 1 : 1 → 2 : 1 generates increasing mechanical tensile strength and decreasing ductility; strength enhancement might be due to entanglements between ORMOSIL and pure silicon oxide phases and side chains. Liquid sorption experiments quantified the affinity of these hybrids for solvents of varying polarity. A dielectric relaxation for the 0 : 1 hybrid at about 1.5 kHz might be related to side chain mobility. A weaker relaxation in the range 10⁴–10⁵ Hz exists for the 0 : 1 and 1 : 1 hybrids and Nafion®-H⁺, but not for the 1 : 0 hybrid that exhibits the behavior ε′ ∼ f⁻ⁿ over a broad frequency (f) range, suggestive of intercluster proton hopping. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:747–763, 1998     

Affinity of Cation-Exchange Membranes Towards Metallic Cations: Application in Continuous Electropermutation

The objective of this work was to correlate the separation process of the metallic cations (M(II)) by electropermutation (EP) of multications solution with the affinity of ion-exchange materials (IEMs). The obtained results show that the affinity order is similar for all tested IEMs and is as follows: Pb(II)>Cd(II)>Zn(II)>Mg(II). Furthermore, the order of the transfer flux (J) of metallic cations obtained with different tested cation-exchange membranes (CEMs) is identical to that encountered for the affinity order. Further analysis of the results demonstrated that the affinity of IEMs and the transfer flux change in reverse order of hydration ionic radius (r) of metallic cations: r_Mg(II)>r_Zn(II)≥r_Cd(II)>r_Pb(II). During the EP, the order of metallic cations transfer is as established previously when using different electro-regeneration cations (H⁺, Na⁺, NH₄⁺) and different co-ions (NO₃^?, Cl^?_, SO₄^2?). However, the extent of the transfer flux as a function of the nature of electro-regeneration cation follows the order: J_M(II)(H⁺)>J_M(II)(NH₄⁺)>J_M(II)(Na⁺). The removal rates of metallic cations vary in the range 89?99%. This work shows that the orders of the IEMs affinity and the transfer are mainly determined by the properties of metallic cations such as the hydration ionic radius. Nevertheless, the importance of the fixation and the transfer of metallic cations depend on the IEMs’ nature.     

Proton Conducting Sulphonated Fluorinated Poly(Styrene) Crosslinked Electrolyte Membranes

Potential membranes for polymer electrolyte membrane fuel cell based on crosslinked sulphonated fluorinated polystyrenes (PS) were synthesised in two steps. First, azide‐telechelic polystyrene was obtained by iodine transfer polymerisation of styrene in the presence of 1,6‐diiodoperfluorohexane followed by azido chain‐end functionalisation. Then azide‐telechelic polystyrene was efficiently crosslinked with 1,10‐diazido‐1H,1H,2H,2H,9H,9H,10H,10H‐perfluorodecane under UV irradiation. After 45 min only, almost completion of azide crosslinking could be achieved, resulting in crosslinked membranes with insoluble fractions higher than 95%. The sulphonation of the crosslinked membranes afforded ionic exchange capacities (IECs) ranging from 2.2 to 3.2 meq g^–1. The hydration number was shown to be very high (from 30 to 75), depending on both the content of perfluorodecane and of sulphonic acid groups. The morphology of the membranes, assessed by small‐angle X‐ray scattering, was found to be a lamellar‐type structure with two types of ionic domains. For the membrane that exhibited an IEC value of 2.2 meq·g^–1, proton conductivity was in the same range as that of Nafion® (120–135 mS·cm^–1), whereas the membrane IEC value of 3.2 meq·g^–1 showed a proton conductivity higher than that of Nafion® in liquid water from 25 to 80 °C, though a high water uptake.     

Sorption and transport properties of the semi‐interpenetrating network based on crosslinked poly(vinyl alcohol) and poly(styrene sulfonic acid‐co‐maleic anhydride) as proton‐conducting membranes

This study investigates the sorption and transport properties of hydrocarbon membranes based on poly(vinyl alcohol) network and poly(styrene sulfonic acid‐co‐maleic acid) (PSSA‐MA). The water and methanol self‐diffusion coefficients through an 80 wt % PSSA‐MA interpenetrating SIPN‐80 membrane measured 3.75 × 10^?6 and 5.47 × 10^?7 cm²/s, respectively. These results are lower than the corresponding values of Nafion® 115 (8.89 × 10^?6 cm²/s for water and 8.63 × 10^?6 cm²/s for methanol). The methanol permeability of SIPN‐80 membrane is 4.1 × 10^?7 cm²/s, or about one‐fourth that of Nafion® 115. The difference in self‐diffusion behaviors of Nafion® 115 and SIPN‐80 membranes is well correlated with their sorption characteristics. The solvent uptake of Nafion® 115 increased as the methanol concentration increased up to a methanol mole fraction of 0.63, and then decreased. However, the solvent uptake of the SIPN‐80 membranes decreased sluggishly as the methanol concentration increased. The λ values of water and methanol (i.e., λ and λ) in Nafion® 115 are quite close, indicating no sorption preference between water and methanol. In contrast, the λ value is only one‐third λ for a SIPN‐80 membrane. Accordingly, the SIPN membranes are regarded as candidates for direct methanol fuel cell applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Poly[poly(oxypropylene) phosphate] macroionophores for transport and separation of cations in a hybrid: Cation‐exchange polymer and liquid membrane system

Poly[poly(oxypropylene) phosphate]s (PPOPP, M_n = 5800, 8100, 10,400), with different POP units (400, 1200, 2000), were synthesized and applied as cation‐selective macroionophores in a multimembrane hybrid system (MHS). The solution of PPOPP in dichloroethane formed the flowing liquid membrane (FLM) circulating between two polymer cation‐exchange membranes, and subsequently, between two polymer‐made pervaporation (PV) membranes. It was found that the PPOPP macroionophores activate the preferential transport of Zn²⁺ cations from aqueous solutions containing competing Cu²⁺, Ca²⁺, Mg²⁺, K⁺, and Na⁺ cations. The following separation orders were observed for PPOPPs with POP‐400 and POP‐1200: Zn²⁺ > Cu²⁺ ? Ca²⁺, Mg²⁺, K⁺, Na⁺, and for PPOPP with POP‐2000: Zn²⁺ > Cu²⁺,Ca²⁺ ? Mg²⁺, K⁺, Na⁺. Always, the particular cations are separated as: Zn²⁺ > Cu²⁺, Ca²⁺ > Mg²⁺, and K⁺ > Na⁺. The properties of PPOPPs were compared to respective transport and separation characteristics corresponding to those of respective poly(propylene glycol)s and poly(oxypropylene) bisphosphates. The results of investigation indicate that the bifunctional character of PPOPPs is caused by the presence of ionizable groups and probably pseudocyclic POP structures. By comparing the separation of cations in the simple MHS[FLM] system and the system supported by pervaporation unit [MHS[FLM‐PV] it was found that continuous dehydration of an organic FLM improves the system overall performance. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1436–1445, 2004     

Vinyl‐addition type norbornene copolymer containing sulfonated biphenyl pendant groups for proton exchange membranes

The vinyl addition type copolymer poly(butoxymethylene norbornene‐co‐biphenyl oxyhexamethyleneoxymethylene norbornene) (P(BN/BphN)) was synthesized by using bis‐(β‐ketonaphthylimino)nickel(II)/B(C₆F₅)₃ catalytic system. P(BN/BphN) was sulfonated to give sulfonated P(BN/BphN) (SP(BN/BphN)) with concentrated sulfuric acid (98%) as sulfonating agent in a component solvent. The ion exchange capacity (IEC), degree of sulfonation (DS), water uptake, and methanol permeability of the SP(BN/BphN)s were increased with the sulfonated time. The methanol permeability of the SP(BN/BphN) membranes was in the range of 1.8 × 10^?7 to 7.5 × 10^?7 cm²/s, which were lower than the value 1.3 × 10^?6 cm²/s of Nafion®115. The proton conductivity of SP(BN/BphN) membranes increased with the increase of IEC values, temperature, and water uptake. Water uptake of the SP(BN/BphN) membranes was lower than that of Nafion® 115 and leads to low proton conduction. Microscopic phase separation occurred in SP(BN/BphN) membrane and domains containing sulfonic acid groups were investigated by SEM and TEM. SP(BN/BphN) membranes had good mechanical properties, high thermal stability, and excellent oxidative stability. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Stabilized heteropolyacid/Nafion composite membranes for elevated temperature/low relative humidity PEFC operation

Organic/inorganic composite membranes with different inorganic heteropolyacid (HPA) additives maintain sufficient proton conductivities for atmospheric pressure elevated temperature (>100 °C) polymer electrolyte fuel cell (PEFC) operation. However, membrane and membrane electrode assembly (MEA) processing is severely curtailed because of the solubility of the HPA additives in aqueous media. Composite membranes with the HPA (phosphotungstic acid; PTA) additive rendered insoluble by ion exchanging protons with larger cations such as Cs⁺, NH₄⁺, Rb⁺ and Tl⁺ were fabricated. The additive loss in aqueous media was lowered from nearly 100% (unmodified HPA) to about 5% (modified HPA). The membranes were robust, and demonstrated low H₂ crossover currents of around 2 mA/cm² for a 28 μm thick membrane. All membranes were evaluated at high temperatures and low relative humidities in an operating fuel cell. The conductivities of the composite membranes at 120 °C and 35% relative humidity were on the order of 1.6 × 10⁻² S/cm.     

Influence of ionic liquid composition on the stability of polyvinyl chloride‐based ionic liquid inclusion membranes in aqueous solution

Membrane technology has gained significant importance with the incorporation of ionic liquids into their structure. This work shows the influence of ionic liquid composition on the stability of PVC‐based polymer ionic liquid inclusion membranes (PILIMs) in aqueous solution. Among the ILs investigated, those membranes which contain between 20 and 30%_w/w of the least soluble, [OMIM⁺][PF₆^?] and [OMIM⁺][Ntf₂^?], exhibit losses of IL lower than 10%. For both ILs, the amount immobilized was maximum for the membranes with 30%_w/w of IL (0.0838 and 0.0832 g, respectively). On the contrary, the ionic liquid loss increases as its solubility in water increase, reaching 99.52% when PILIMs are prepared with 70%_w/w of [OMIM⁺][BF₄^?]. The results demonstrate that the stability of PILIMs depends on the solubility of the IL in the surrounding phase and the specific interaction between the IL and the polymeric support for PVC‐to‐IL ratios higher than 30%_w/w. © 2016 American Institute of Chemical Engineers AIChE J, 63: 770–780, 2017     

Sulfonated poly(ether sulfone)/silica composite membranes for direct methanol fuel cells

A series of sulfonated poly(ether sulfone) (SPES)/silica composite membranes were prepared by sol–gel method using tetraethylorthosilicate (TEOS) hydrolysis. Physico–chemical properties of the composite membranes were characterized by thermogravimetric analysis (TGA), X‐ray diffraction (XRD), scanning electron microscope–energy dispersive X‐ray (SEM–EDX), and water uptake. Compared to a pure SPES membrane, SiO₂ doping in the membranes led to a higher thermal stability and water uptake. SEM–EDX indicated that SiO₂ particles were uniformly embedded throughout the SPES matrix. Proper silica loadings (below 5 wt %) in the composite membranes helped to inhibit methanol permeation. The permeability coefficient of the composite membrane with 5 wt % SiO₂ was 1.06 × 10^?7 cm²/s, which was lower than that of the SPES and just one tenth of that of Nafion® 112. Although proton conductivity of the composite membranes decreased with increasing silica content, the selectivity (the ratio of proton conductivity and methanol permeability) of the composite membrane with 5 wt % silica loading was higher than that of the SPES and Nafion® 112 membrane. This excellent selectivity of SPES/SiO₂ composite membranes could indicate a potential feasibility as a promising electrolyte for direct methanol fuel cell. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Sulfonated polyimide and poly (ethylene glycol) diacrylate based semi‐interpenetrating polymer network membranes for fuel cells

Semi‐interpenetrating polymer network (semi‐IPN) membranes based on novel sulfonated polyimide (SPI) and poly (ethylene glycol) diacrylate (PEGDA) have been prepared for the fuel cell applications. SPI was synthesized from 1,4,5,8‐naphthalenetetracarboxylic dianhydride, 4,4′‐diaminobiphenyl 2,2′‐disulfonic acid, and 2‐bis [4‐(4‐aminophenoxy) phenyl] hexafluoropropane. PEGDA was polymerized in the presence of SPI to synthesize semi‐IPN membranes of different ionic contents. These membranes were characterized by determining, ion exchange capacity, water uptake, water stability, proton conductivity, and thermal stability. The proton conductivity of the membranes increased with increasing PEGDA content in the order of 10^?1 S cm^?1 at 90°C. These interpenetrating network membranes showed higher water stability than the pure acid polyimide membrane. This study shows that semi‐IPN SPI membranes based on PEGDA which gives hydrophilic group and structural stability can be available candidates comparable to Nafion® 117 over 70°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Modification of poly acrylic acid using calix[4]arene derivative for the adsorption of toxic heavy metals

Poly acrylic acid (PAA) was grafted with p‐t‐butyl calix[4]arene diamine (distal cone) (2) to adsorb toxic heavy metal and alkali metal cations. The grafting method includes the amidation reaction of PAA with calixarene diamine derivative 2 which was carried out in N,N‐dimethylformamide (DMF) and N–methyl‐2‐pyrrolidone (NMP) as solvents. The modified PAAs (PAA‐C1 and PAA‐C2) were characterized by FTIR, ¹H‐NMR, thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). PAA‐C1 and PAA‐C2 were used to evaluate the sorption properties of some toxic heavy metal cations (Co²⁺, Cu²⁺, Cd²⁺, Hg²⁺), alkali metal cations (Na⁺, K⁺, Cs⁺), and Ag⁺. Results showed that the modified PAAs were good sorbents for heavy metal and alkali metal cations. The main goal of this project is to design hydrophobically modified PAA that is suitable for ion selective membranes and chemical sensor devices for adsorption of toxic heavy metals. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Water Free Operated Phosphoric Acid Doped Radiation‐Grafted Proton Conducting Membranes for High Temperature Polymer Electrolyte Membrane Fuel Cells

The present study uses the radiation‐induced grafting method and applies it onto poly(ethylene‐alt‐tetrafluoroethylene) (ETFE) for the synthesis of proton‐exchange membranes by using monomers 4‐vinyl pyridine (4VP), 2‐vinyl pyridine (2VP), N‐vinyl‐2‐pyrrolidone (NVP) followed by phosphoric acid doping. Phosphoric acid that provides Grotthuss mechanism in proton mobilization is used to transform the graft copolymers to a high temperature membrane state. Resultant proton‐exchange membranes are verified with their proton conductivity, water uptake, mechanical and thermal properties, and phosphorous distribution as ex situ characterization. Our most important finding as a novelty in literature is that ETFE‐g‐P4VP phosphoric acid doped proton‐exchange membranes exhibit proton conductivities as 66 mS cm^–1 at 130 °C, 53 mS cm^–1 at 120 °C, 45 mS cm^–1 at 80 °C at RH 100% and 55 mS cm^–1 at 130 °C, 40 mS cm^–1 at 120 °C, 35 mS cm^–1 at 80 °C at dry conditions. Moreover, ETFE‐g‐P4VP membranes still conserves the mechanical properties, i.e., tensile strength up to 48 MPa. ETFE‐g‐P4VP membranes were tested in PEMFC at 80, 100, and 120 °C and RH <2% and exhibit promising performance as an alternative to commercial Nafion® membranes. The single cell testing performance of ETFE‐g‐P4VP membranes is presented for the first time in literature in our study.     

Evaluating the Effectiveness of Using Flexography Printing for Manufacturing Catalyst‐Coated Membranes for Fuel Cells

This study is an evaluation of the effectiveness of the flexography printing process for manufacturing catalyst‐coated membranes (CCMs) for use in proton exchange membrane fuel cells (PEMFCs). Flexography is a maskless and continuous process that is used in large‐scale production with water‐based inks to reduce the cost of production of PEMFC components. Unfortunately, water has undesirable effects on the Nafion® membrane: water wets the membrane surface poorly and causes the membrane to bulge outwards significantly. Membrane printability was improved by pre‐treating membrane samples by water immersion for short periods (<2 min). This pre‐treatment was used to control the membrane deformation before printing to limit the impact of the ink transfer. Water and ink drop deposition experiments were performed to estimate the liquid‐air‐Nafion® apparent contact angle and the locally induced membrane deformation. Despite the short immersion times used in the tests, the immersion pre‐treatment appeared to induce structural modifications that enhanced both the membrane wettability and the dimensional stability. Flexography printability tests were performed on these treated membranes and showed that the dimensional instability of the Nafion® membrane was the critical parameter for limiting the ink transfer. The immersion pre‐treatment improved the printability of the Nafion® membranes, which were used to fabricate cathodes that were tested in an operational fuel cell.     

Sulfonated poly(arylene ether ketone)s prepared by direct copolymerization as proton exchange membranes: Synthesis and comparative investigation on transport properties

Sulfonated poly(aryl ether ketone)s (SPAEK) copolymers were synthesized by aromatic nucleophilic polycondensation from 3,3′, 5,5′‐tetramethyl‐4, 4′–biphenol, 1,4‐bis(4‐fluorobenzoyl) benzene, and disulfonated difluorobenzophenone. The SPAEK membranes did not exhibit excessive swelling in hot water and at the same time show the proton conductivities in the range of 0.030 S/cm to 0.099 S/cm at 80°C. The methanol diffusion coefficients of the SPAEK membranes were in the range of 4.7 × 10^?7 to 8.1 × 10^?7cm²/s measured at 25°C. The transport properties of this series of SPAEK copolymers were compared to poly(aryl ether ether ketone)s (SPEEK), poly(aryl ether ether ketone ketone)s (SPEEKK), and Nafion® membranes. It was found that the transport properties (including proton conductivity and methanol permeability) follows the trend of SPEEKK‐60 < SPAEK‐60 < SPEEK‐60 < Nafion® 117, the order of which is also attributed to the differences in the chemical structure of the polymers and the membrane morphology. In general, this novel series of SPAEK membranes possess various advantages, such as low cost of the initial monomers, high thermal and mechanical stability, and low methanol permeability while simultaneously possessing sufficient proton conductivity, which makes them notably promising as proton exchange membrane (PEM) materials in direct methanol fuel cell (DMFC) applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008