Methanol Permeability Coefficient Research Articles

Highly Conductive Polyelectrolyte Membranes Poly(vinyl alcohol)/Poly(2-acrylamido-2-methyl propane sulfonic acid) (PVA/PAMPS) for Fuel Cell Application.

In this study, chemically cross-linked PVA/PAMPS membranes have been prepared to be used in direct methanol fuel cells (DMFCs). The structural properties of the resultant membrane were characterized by use FTIR and SEM. Additionally, their thermal stability was assessed using TGA. Moreover, the mechanical properties and methanol and water uptake of membrane was studied. The obtained FTIR of PVA/PAMPS membranes revealed a noticeable increase in the intensity of adsorption peaks appearing at 1062 and 1220 cm−1, which correspond to sulfonic groups with the increasing proportion of PAMPS. The thermograms of these polyelectrolyte membranes showed that their thermal stability was lower than that of PVA membrane, and total weight loss gradually decreased with increasing the PAMPS. Additionally, the functional properties and efficiency of these polyelectrolyte membranes were significantly improved with increasing PAMPS proportion in these blends. The IEC of polymer blend membrane prepared using PVA/PAMPS ratio of 1:1 was 2.64 meq/g. The same membrane recorded also a methanol permeability coefficient of 2.5 × 10−8 cm2/s and thus, its efficiency factor was 4 × 105 greater than that previously reported for the commercial polyelectrolyte membrane, Nafion® (2.6 × 105). No significant increase in this efficiency factor was observed with a further amount of PAMPS. These results proved that the PVA:PAMPS ratio of 1:1 represents the optimum mass ratio to develop the cost-effective and efficient PVA/PAMPS blend membranes for DMFCs applications.

UiO-66-NH2 functionalized cellulose nanofibers embedded in sulfonated polysulfone as proton exchange membrane

Metal–organic frameworks (MOFs) exhibit high proton conductivity, thermal stability, and offer immense flexibility in terms of tailoring their size. Owing to their unique characteristics, they are desirable candidates for proton conductors. Nevertheless, constructing ordered MOF proton channels in proton exchange membranes (PEMs) remains a formidable challenge. Herein, blend nanofibers of cellulose and UiO-66-NH2 (Cell–UiO-66-NH2) obtained via the electrospinning process were embedded in a sulfonated polysulfone matrix to obtain high-performance composite PEMs with an orderly arrangement of UiO-66-NH2. Comprehensive characterization and membrane performance tests reveal that composite membrane with 5 wt% (nominal) UiO-66-NH2 have revealed high proton conductivity of 0.196 S cm−1 at 80 °C and 100% relative humidity. Meantime, the composite membrane exhibits a low methanol permeability coefficient (~5.5 × 10−7 cm2 s−1). Moreover, the composite membrane exhibits a low swelling ratio (17.3%) even at 80 °C. The Cell–UiO-66-NH2 nanofibers exhibit strong potential for use as a proton-conducting nanofiller in fuel-cell PEMs.

Sulfonated poly (arylene ether sulfone)-graft-sulfonated poly (vinyl alcohol) proton exchange membranes: Improved proton selectivity

Aldehyde terminated sulfonated poly (arylene ether sulfone) (SPAES-CHO) is prepared by a series of nucleophilic substitution reaction based on SPAES in this paper. Novel SPAES-graft-SPVA (SPAES-g-SPVA) membranes are fabricated by acetal reaction between SPAES-CHO and different amounts of sulfonated poly (vinyl alcohol) (SPVA). The 1H-NMR and FTIR indicate the successful preparation of SPAES-CHO and SPAES-g-SPVA membranes. With the introduction of SPVA, the SPAES-g-SPVA membranes have much lower methanol permeability than pure SPAES membrane and Nafion117 membrane. The methanol permeability coefficients of the SPAES-g-SPVA membranes decrease from 3.41 × 10−7 cm2 s−1 to 1.67 × 10−7 cm2 s−1 with the increase of SPVA content. And the proton conductivity of all the membranes is higher than 15 mS cm−1 at 25°C. Moreover, SPAES-g-SPVA membranes exhibit high proton selectivity. Especially, SPAES-g-SPVA-30% membrane has the highest proton selectivity, which is nearly five times higher than Nafion117.

Amino acid-functionalized metal organic framework with excellent proton conductivity for proton exchange membranes

Proton conduction is a ubiquitous fundamental phenomenon in biological systems. Biology has solved the problem of energy-related proton conduction, in which the exposed amino acids in the protein ordered channels play a key role in proton conduction. In this contribution, amino acids (glutamate, lysine, and threonine) were attached to metal organic framework (MOF) nanoparticles, which were incorporated into sulfonated polysulfone matrix forming bio-proton channels for the nanocomposite membranes. It is shown in the results that the amino acid-functionalized MOF can help to enhance the proton conductivity and the proton exchange membrane with glutamate-functionalized MOF demonstrate excellent proton conductivity of 0.212 S cm−1 at 80 °C and 100% relative humidity. Meanwhile, the methanol permeability coefficient of the nanocomposite membrane is reduced to 5.8 × 10−7 cm2 s−1. The nanocomposite membranes demonstrate excellent proton conductivity, dimensional stabilities, water absorption, and resistance to methanol performance. Therefore, this material is promising for fuel cells.

Synthesis and characterization of a crosslinked membrane based on sulfonated poly(aryl ether sulfone) and sulfonated polyvinyl alcohol applied in direct methanol fuel cells

Vinyl-terminated sulfonated poly (arylene ether sulfone) (VSPAES) and sulfonated polyvinyl alcohol containing vinyl group (VSPVA) have been prepared. The VSPVA and VSPAES were crosslinked by adding AIBN as initiator. The results of FT-IR and 1H-NMR indicated the existence of sulfonic acid groups and crosslinked structure in these crosslinked membranes. The microphase structures of the membranes are analyzed by SEM. The proton conductivities of membranes were above 10 mS cm−1, which indicated that it basically meet the needs of fuel cells. The methanol permeability coefficients of CSPAES membrane is 2.8 × 10–7 cm2 s−1, remarkably lower than neat SPAES (8.5 × 10–7 cm2 s−1) and Nafion117 (14.1 × 10–7 cm2 s−1). Moreover, the proton selecticity of CSPAES membrane is close to 2 times higher than that of Nafion 117 membrane. The crosslinked membrane showed better stability than the linear SPAES membrane.

PEMs with high proton conductivity and excellent methanol resistance based on sulfonated poly (aryl ether ketone sulfone) containing comb-shaped structures for DMFCs applications

Sulfonated poly (aryl ether ketone sulfone) polymers (SPAEKS-PSA X) with the comb-shaped structure were prepared by grafting with 1, 3-propanesultone (PSA). The successful synthesis of SPAEKS-PSA X was confirmed by the FT-IR spectra. The morphology of the membrane was investigated by the small angle X-ray scattering and the transmission electron microscopy. The nanophase separation was brought in a comb-shaped structure between the main chains and the propyl sulfonic acid groups. The SPAEKS-PSA 15 membrane exhibited the highest conductivity of 101 mS cm−1 under 80 °C and 100% relative humidity conditions (100% RH). In addition, the methanol permeability coefficients of SPAEKS-PSA X membranes (7.56 × 10−7 to 9.44 × 10−7 cm2 s−1) were much lower compared to Nafion®117 (22.37 × 10−7 cm2 s−1). Meanwhile, the SPAEKS-PSA X membranes also displayed excellent mechanical properties (tensile modulus >30 MPa), thermal, oxidative stabilities and fuel cell performance. Considering the parameters above, especially the elevated proton conductivities as well as high methanol resistance, the comb-shaped structure is a promising design for DMFCs applications.

4-Aminopyridine grafted sulfonated poly(arylene ether ketone sulfone) proton exchange membrane with high relative selectivity for fuel cells

A series of sulfonated poly(arylene ether ketone sulfone)s polymer having a degree of sulfonation of 80% and a carboxyl group in the side chain (C-SPAEKS) were prepared by polycondensation. The 4-aminopyridine grafted sulfonated poly(arylene ether ketone sulfone)s polymer membranes (SPPs) were prepared by amidation reaction with the carboxyl group to immobilize 4-aminopyridine on the side chain. The 1H NMR results and Fourier transform infrared of SPP membranes demonstrated the successful grafting of the 4-aminopyridine. Proton conductivity, water absorption, swelling ratio, and thermal stability of different proportions of SPP membranes were investigated under the different conditions. With the increase of pyridine grafting content, the methanol permeability coefficient of the membrane decreased significantly from 8.17 × 10−7 cm2s−1 to 8.92 × 10−8 cm2s−1 at 25 °C. And, the proton conductivity and relative selectivity of the membrane were positively correlated with the grafted pyridine content. Among them, the SPP-4 membrane exhibited the highest proton conductivity of 0.088 Scm−1 at 100 °C. The relative selectivity increased from 4.73 × 104 S scm−3 to 9.84 × 104 S scm−3.

Proton exchange membranes with cross-linked interpenetrating network of sulfonated polyvinyl alcohol and poly(2-acrylamido-2-methyl-1-propanesulfonic acid): Excellent relative selectivity

Cross-linked interpenetrating composite membranes of sulfonated polyvinyl alcohol and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (SPVA/PAMPS) were prepared for application in direct methanol fuel cells (DMFCs). SPVA was synthesized using sulfuric acid to sulfonate the hydroxyl groups of PVA. Sulfosuccinic acid (SSA) and N,N′-methylenebis(acrylamide) (MBA) were used as the crosslinking agents to form the Cross-linked interpenetrating network structure by thermal crosslinking reaction and free-radical polymerization, respectively. The mechanical property, oxidative stability, and proton conductivity of SPVA/PAMPS composite membranes improved significantly with increasing content of AMPS. Especially, the proton conductivity of SPVA/PAMPS-40% membrane was excellent, i.e., 0.146 S cm−1 at 100 °C. Furthermore, the Cross-linked interpenetrating network structure decreased the methanol crossover of composite membranes. The methanol permeability coefficient of SPVA/PAMPS-40% membrane was 11.3 × 10−7 cm2 s−1 at 60 °C. The composite membranes showed better relative selectivity than pure SPVA membrane, the relative selectivity of SPVA/PAMPS-40% membrane was 7.43 × 104 S scm−3 at 60 °C. This study provides a method to synthesize inexpensive and readily prepared proton exchange membranes for DMFC applications.

Synthesis and properties of novel cross-linked composite sulfonated poly (aryl ether ketone sulfone) containing multiple sulfonic side chains for high-performance proton exchange membranes

The synthesis and properties of novel cross-linked composite sulfonated poly (aryl ether ketone sulfone) containing multiple sulfonic side chains as proton exchange membranes were investigated. The multiple side-chain membranes were prepared by direct polycondensation and simple free radical reaction. The cross-linked composite membranes were prepared by solvent coating method. The prepared membranes showed lower water absorption and swelling ratio than that of Nafion 117. The S-Am-2.0/C exhibited the highest proton conductivity of 0.135 S cm−1 at 80 °C, while its swelling ratio was only 3.59% at the same temperature. Much lower methanol permeability coefficients in the range of 3.11 × 10−8 cm2 s−1–7.25 × 10−7 cm2 s−1 compared to Nafion 117 (2.29 × 10−6 cm2 s−1) were also observed for the prepared membranes. Moreover, the S-Am-2.0/C exhibited higher peak power density (121.09 mW cm−2) than that of main-chain type C-SPAEKS membrane (66.65 mW cm−2). The results indicate that the cross-linked composite membranes are good candidate for fuel cells.

Enhanced proton conductivity and relative selectivity of sulfonated poly(arylene ether ketone sulfone) proton exchange membranes by using triazole-grafted 3-Glycidyloxypropyltrimethoxysilane

Herein, we demonstrate the fabrication of cross-linked membranes based on sulfonated poly(arylene ether ketone sulfone) containing pendant amino groups (AM-SPAEKS) and triazole-grafted 3-Glycidyloxypropyltrimethoxysilane (GT) cross-linkers by a sol-gel process, then the obtained cross-linked membranes are named as AMSP/GT membranes. The GT cross-linkers are synthesized by the ring-opening reaction of the epoxy group and 3-amino-1,2,4-triazole. The AMSP/GT cross-linked membranes exhibit excellent thermal, oxidation and dimensional stability. Furthermore, the AMSP/GT membranes possess a low methanol permeability coefficient (9.95 × 10−7 cm2 s−1 at 60 °C) due to the formation of cross-linked network structures. In addition, the proton conductivity and relative selectivity of the AMSP/GT membranes are higher, at elevated temperatures (>80 °C), than AM-SPAEKS membranes. The highest proton conductivity of 0.135 S cm−1 is demonstrated, for the AMSP/GT-30 membrane, at 100 °C. The relative selectivity of AMSP/GT-30 can reach 7.54 × 104 S scm−3 which is three times higher than that of the AM-SPAEKS, at 60 °C. These results indicate that the AMSP/GT membranes can be promising candidates for practical applications such as proton exchange fuel cells etc.

Facile synthesis of metal oxide nanofibers and construction of continuous proton-conducting pathways in SPEEK composite membranes

In this study, a facile approach was used to prepare hydrophilic TiO2 nanofibers (TiNFs) by calcining electrospun polyacrylonitrile nanofibers embedded with titanium precursors. A high-performance proton exchange membrane (PEM) was achieved by incorporating the TiNFs into a sulfonated poly(ether ether ketone) (SPEEK) matrix. The high aspect ratios of the inorganic nanofibers permitted interconnecting of ion-conducting channels, thereby significantly improving proton conductivity in the membrane. In addition, the TiNFs provided tortuous pathways for methanol transport, suppressing the methanol permeability coefficient. The maximum power density of the SPEEK/TiNFs-1.0 composite membrane was 1.4 times higher than that of the pristine SPEEK membrane at 100% relative humidity and 60 °C. Furthermore, the stable fiber skeleton improved the mechanical stability of the composite membrane. The SPEEK/TiNFs-1.0 membrane exhibited superior mechanical properties with the tensile strength of 40.4 MPa and maximum elongation at break of 76%.

Cross-linked sulfonated poly(arylene ether nitrile)s with high selectivity for proton exchange membranes

For the purpose of prepare a high performance proton exchange membrane with low methanol permeability and high proton conductivity, a sulfonated poly(arylene ether nitrile)s (SPEN) with carboxyl groups were synthesized. Then the cross-linked membranes were prepared by simply thermal curing in which the polymer network structures were covalent cross-linked. The chemical structures of the cross-linked membranes were characterized by Fourier transform infrared analysis. The resulting cross-linked membranes can effectively reduce water uptake, swelling ratio and methanol permeability. Among the cross-linked membranes, CSPEN-70 exhibits low water uptake, low swelling ratio (135.4% and 23.8% at 80°C, respectively) and low methanol permeability coefficient (3.23×10−7cm2·s−1), while maintaining proton conductivity of 0.148S·cm−1. More importantly, the selectivity of cross-linked CSPEN-70 is about 5 times higher than that of Nafion117. All the data prove that the cross-linked membranes may be potential proton exchange membrane for the direct methanol fuel cells (DMFCs) application.

Influence of alkaline 2D carbon nitride nanosheets as fillers for anchoring HPW and improving conductivity of SPEEK nanocomposite membranes

In the present study, novel composite membranes were prepared based on sulfonated poly (ether ether ketone)/phosphotungstic acid/carbon nitride nanosheets (SPEEK/HPW/g-C3N4). The alkaline ultrathin g-C3N4 nanosheets in the membranes behaved like “double-sided adhesive”, forming hydrogen bonds with the HPW molecules to anchor hydrophilic HPW without leaking. Moreover, the amine groups of nanosheets formed acid–base pairs with –SO3H of the SPEEK polymer matrix, facilitating the Grotthuss-type transport of proton to improve conductivity. The g-C3N4 inorganic particles provided tortuous pathways for methanol transport to suppress the methanol permeability coefficient. The selectivity of the SPEEK/HPW/g-C3N4-1.0 was 2.3 times higher than that of SPEEK/HPW and 1.5 times higher than that of pristine SPEEK. SPEEK/HPW/g-C3N4 hybrid membranes exhibited stable and durable operation for 240 h under 100% RH at 60 °C. Moreover, membranes exhibited superior mechanical property, with maximum elongation at break of 223.3%.

Phthalonitrile-terminated sulfonated poly(arylene ether nitrile)s for direct methanol fuel cells (DMFCs) application

To improve the dimensional stability and methanol resistance, a novel phthalonitrile-terminated sulfonated poly(arylene ether nitrile)s (SPENs) to prepare cross-linked membranes for direct methanol fuel cells (DMFCs) application has been successfully implemented. Compared with SPENs, cross-linked membranes exhibited lower water uptake, swelling ratio, and methanol permeability coefficient. For example, the water uptake and swelling ratio of SPEN-70 were 50.3 wt.% and 17.0% as the values of cross-linked sulfonated poly(arylene ether nitrile)s (CSPEN)-70 were merely 15.4 wt.% and 3.2% at 20 °C. The methanol permeability of SPEN-70 was 6.7 × 10−7 cm2 s−1 as the values of CSPEN-70 were merely 1.4 × 10−7 cm2 s−1, which were all much lower than that of Nafion 117 (1.41 × 10−6 cm2 s−1) as expected. Although the proton conductivity of CSPEN slightly decreased by the introduction of cross-linked structure, it possessed higher selectivity than the SPEN and Nafion 117 due to their lower methanol permeability. The cross-linked SPEN-50 (CSPEN-50) membrane exhibited the highest selectivity, which about 30.7 times higher compared with that of Nafion 117.

Chemically stable thioether cross-linked membranes derived from sulfonated poly(arylene ether ketone)s for direct methanol fuel cells

A series of thioether cross-linked membranes based on sulfonated poly(arylene ether ketone)s containing propenyl groups were prepared to solve the problem of high methanol permeability for proton electrolyte membrane in direct methanol fuel cells (DMFCs). For this purpose, 4,4′-thiobisbenzenethiol was selected as cross-linker, and the cross-linked structure was formed via thiol-ene click chemical reaction between propenyl and thiol groups. Compared with pristine membrane, the thioether cross-linked membranes exhibited improved mechanical properties and dimensional stabilities. As the cross-linker increased, the swelling ratio decreased from 11.01% to 8.64% at 20°C and from 15.18% to 10.69% at 80°C. Furthermore, the modified membranes exhibited reduced methanol permeability coefficients (down to 4.03 × 10−7 cm2 s−1), which was nearly half of the pristine membrane (7.66 × 10−7 cm2 s−1). Due to the thioether units, the cross-linked membranes showed enhanced oxidative stabilities, and the longest elapsed time in Fenton’s reagent was 225 min, which was 2.5 times longer than that of pristine polymeric membrane. Although the proton conductivity decreased upon the addition of cross-linker agent, the selectivity value increased due to the lower methanol permeability. Thus, all the results implied that the thioether cross-linked membranes were promising alternative materials for DMFCs application.

Excellent performance of resistance methanol of a novel sulfonated poly (aryl ether ketone sulfone)/poly (vinylalcohol) composite membrane for direct methanol fuel cell applications

Composite membrane comprised of the sulfonated poly (aryl ether ketone sulfion) with amino groups (Am-SPAEKS) and poly (vinylalcohol) (PVA) was successfully prepared by the co-solvent coating method. The composite membranes perform a variety of advantages, such as good thermal stability, outstanding water retention, stable mechanical performance and oxidative stability, and the composite membranes have superior water uptake. The proton conductivity of Am-SPAEKS-PVA50% was 0.041 S cm−1 at 80 °C and 0.038 S cm−1 at 120 °C, and the methanol permeability coefficient of the composite membranes was 2.95 × 10−7 at 25 °C and 8.26 × 10−7 cm2 s−1, far below the methanol permeability coefficient of Nafion (25.1 × 10−7 cm2 s−1 at 25 °C), so that it could ensures prevent methanol permeation effectively, improve the utilization of methanol. Moreover, the composite membranes show fairly ideal selectivity. These excellent performances show that the composite membranes could be served as new potential membrane materials for direct methanol fuel cells.

Preparation and evaluation of crosslinked sulfonated polyphosphazene with poly(aryloxy cyclotriphosphazene) for proton exchange membrane

Several crosslinked proton exchange membranes with high proton conductivities and low methanol permeability coefficients were prepared, based on the sulfonated poly[(4-fluorophenoxy)(phenoxy)] phosphazene (SPFPP) and newly synthesized water soluble sulfonated poly(cyclophosphazene) (SPCP) containing clustered flexible pendant sulfonic acids. The structure of SPCP was characterized by fourier transform infrared spectroscopy (FTIR) and 1H NMR spectra. The membranes showed moderate proton conductivities and much lower methanol permeability coefficients when compared to Nafion 117. Transmission electron microscopy (TEM) results indicated the well-defined phase separation between the locally and densely sulfonated units and hydrophobic units, which induced efficient proton conduction. In comparison with SPFPP membrane, the proton conductivities, oxidative stabilities and mechanical properties of crosslinked membranes remarkably were improved. The selectivity values of all the crosslinked membranes were also much higher than that of Nafion 117 (0.74×105S·s/cm3). These results suggested that the cSPFPP/SPCP membranes were promising candidate materials for proton exchange membrane in direct methanol fuel cells.

Direct polymerization of a novel sulfonated poly(arylene ether ketone sulfone)/sulfonated poly(vinylalcohol) crosslinked membrane for direct methanol fuel cell applications

Sulfonated poly(arylene ether ketone sulfone) copolymers containing carboxylic acid groups (C-SPAEKS) were prepared by direct aromatic nucleophilic substitution polymerization. Novel C-SPAEKS-based crosslinked membranes containing different amounts of sulfonated poly(vinyl alcohol) (SPVA) were fabricated. The Fourier transform infrared and 1H NMR analyses showed the presence of carboxylic acid and sulfonic acid groups, as well as ester bonds in the crosslinked membranes. As expected, the crosslinked membranes exhibited enhanced thermal stability relative to the uncrosslinked membranes. Both the atomic force microscopy (AFM) and transmission electron microscopy (TEM) images clearly show the hydrophilic domains and hydrophobic polymer backbone. The methanol permeability coefficients of the crosslinked membranes with the SPVA content from 10% to 90% ranged from 10.67×10−7cm2s−1 to 1.05×10−7cm2s−1 at 25°C, and from 22.24×10−7cm2s−1 to 2.41×10−7cm2s−1 at 60°C, which are much lower than those of C-SPAEKS membrane (12.79×10−7cm2s−1 at 25°C and 26.85×10−7cm2s−1 at 60°C). The proton conductivities of all the crosslinked membranes were above 10−2Scm−1, satisfying the requirement of fuel cells. Furthermore, the crosslinked membranes exhibited a high selectivity, further confirming that this series of crosslinked membranes are potential candidates as new polymeric electrolyte materials for direct methanol fuel cells.

Fabrication of sulfonated poly(aryl ether ketone sulfone) membranes blended with phosphotungstic acid and microporous poly(vinylidene fluoride) as a depository for direct-methanol fuel cells

A series of sulfonated poly(aryl ether ketone sulfone)/poly(vinylidene fluoride) phosphotungstic acid (SPAEKS/PVDF-HPW) composite membranes were prepared and characterized by Fourier transform infrared spectroscopy. No phase separation was observed by scanning electron microscopy. The HPW particles are evenly dispersed in the membranes, probably because the microporous structure of PVDF stabilized the dispersion of HPW particles in the membranes. Thermogravimetric analysis showed that the thermal stability of the membranes increased with increase in HPW content. Moreover, the composite membranes exhibited outstanding oxidative stability. The methanol permeability coefficient of the SPAEKS/PVDF-HPW10% membrane at 20 °C was 1.68 × 10−7 cm2 s−1, and the highest proton conductivity of the membrane at 80 °C was 0.098 S cm−1, slightly lower than that of Nafion® 117. However, the relative selectivity of the membrane was higher than that of Nafion® 117. The swelling ratio of the membrane at 80 °C was 16%, and the methanol uptake of the membrane at room temperature was only 10.2%, much lower than those of Nafion® 117. The results indicate that the SPAEKS/PVDF-HPW membranes can be used as an alternative proton exchange membrane for direct-methanol fuel cells.

Synthesis and properties of sulfonated poly(phosphazene)‐graft‐poly(styrene‐co‐N‐benzylmaleimide) copolymers via atom transfer radical polymerization for proton exchange membrane

ABSTRACTA series of sulfonated poly(phosphazene)‐graft‐poly(styrene‐co‐N‐benzylmaleimide) (PP‐g‐PSN) copolymers were prepared via atom transfer radical polymerization (ATRP), followed by regioselective sulfonation which occurred preferentially at the poly(styrene‐co‐N‐benzylmaleimide) sites. The structures of these copolymers were confirmed by Fourier transform infrared (FTIR) spectroscopy, 1H‐NMR, and 31P‐NMR, respectively. The resulting sulfonated PP‐g‐PSN membranes showed high water uptakes (WUs), low water swelling ratios (SWs), low methanol permeability coefficients, and proper proton conductivities. In comparison with non‐grafting sulfonated poly(bis(phenoxy)phosphazene) (SPBPP) membrane previously reported, the present membranes displayed higher proton conductivity, significantly improved the thermal and oxidative stabilities. Transmission electron microscopy (TEM) observation showed clear phase‐separated structures resulting from the difference in polarity between the hydrophobic polyphosphazene backbone and hydrophilic sulfonated poly(styrene‐co‐N‐benzylmaleimide) side chains, indicating effective ionic pathway in these membranes. The results showed that these materials were promising candidate materials for proton exchange membrane (PEM) in direct methanol fuel cell (DMFC) applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42251.