High pH Environment Research Articles

Hydroxide-ion induced degradation pathway for dimethylimidazolium groups in anion exchange membranes

The alkaline stability of imidazolium-based anion exchange membranes was studied by FT-IR and 13C solid state NMR. Imidazolium groups are susceptible to attack by hydroxide ions and undergo degradation in alkaline conditions through a ring-opening mechanism. Density functional theory (DFT) studies were performed to better understand the degradation pathway and the relative stability of imidazolium cations on exposure to hydroxide. The ring-opening degradation pathway follows the following three steps: (a) a nucleophilic reaction, (b) a ring-opening reaction, and (c) a rearrangement reaction. The structural changes induced in the imidazole ring were studied using a model of the dimethylimidazolium cation ([DMIM]+). The energy changes along the degradation pathway were obtained from reaction path calculations. The effect of hydroxide ion concentration and dielectric constant of surrounding medium on reaction energy barriers were studied. The hydroxide-ion induced degradation of the dimethylimidazolium cation was found to be more facile in high-pH environments. Good solvation of the dimethylimidazolium cation and the hydroxide ion was helpful in minimizing the degradation and enhancing the chemical stability of anion exchange membranes based on these cations.

Fungal but not bacterial soil communities recover after termination of decadal nitrogen additions to boreal forest

The rate at which formerly nitrogen loaded forests will return to their natural nitrogen-limited state is of considerable scientific and societal interest. Yet the sensitivity of soil microorganisms to these putative changes is mainly unknown. We report effects on fungal and bacterial communities caused by two decades of chronic nitrogen fertilization and subsequent changes 14 years after termination of nitrogen load. We compare these changes in community composition with those observed in natural nitrogen supply and pH gradients using DNA fingerprinting methods and Sanger sequencing.Soil fungal ITS length-heterogeneity profiles correlated equally well to carbon-to-nitrogen ratios and pH. Sequencing results indicated a clear decrease in the relative abundance of amplicons ascribed to known ectomycorrhizal fungi in both natural and experimental high nitrogen conditions, and a recovery of species in the terminated nitrogen treatment. The dominant sequences in low nitrogen soils were identified as members of Piloderma spp. Terminal restriction fragment length profiles of the bacterial 16S rRNA gene were linked to carbon-to-nitrogen ratios and pH in the natural locations but to soil nitrogen in the nitrogen addition experiment that had low variability in pH. Sequencing revealed the dominance of Acidobacteria and Proteobacteria in all soils but also showed a marked increase in Bacteroidetes in high nitrogen treatment not evident in the natural high nitrogen and high pH environments. Proteobacteria sequences included described strains from high-organic and low-pH systems that are believed be involved in degradation of complex plant material.There were signs of recovery of fungal but not of bacterial communities in the sense that community's in terminated nitrogen addition plots did not differ significantly from those in control plots or from the low nitrogen stands in the natural nitrogen supply gradient. The need of further examination of the seemingly functionally redundant bacterial communities is stressed.

Reexamination of Lime Stabilization Mechanisms of Expansive Clay

For the purpose of understanding the mechanism that results from treating expansive soil with lime, a series of tests were conducted on selected Nanyang expansive clay. X-ray diffraction tests indicated that the major clay minerals of Nanyang expansive clay are a mixture of illite and smectite with some kaolinite and chlorite. The scanning electron microscope images obtained at different curing times were used to interpret the change in the microstructure and the formation of new products from the lime treated samples. The atomic absorption method was adopted to test the concentration of Ca2+ and K+ in the pore water and exchange complex of lime treated Nanyang expansive clay. The results indicate that (1) cation exchange, ions crowding, formation of Ca(OH)2·nH2O, agglomeration, and breaking of clay particles in a high pH environment are the dominant reactions in the early stage of treating expansive clay with lime; and (2) the pozzolanic reaction and carbonation occurred at a late stage after lime treatment (90 days in this study).

Investigating the mechanism of stress corrosion cracking in near-neutral and high pH environments for API 5L X52 steel

Stress corrosion cracking behaviour of API-5L-X52 steel under cathodic protection in near-neutral and high pH conditions was studied using slow strain rate test method and electrochemical measurements. The slow strain rate test showed ductile and brittle fracture feature at low and high applied potentials, respectively. In order to identify the mechanism contributes in stress corrosion cracking; the electrochemical potentiodynamic polarisation test was done at fast and slow sweep rate. The results revealed that at near-neutral pH condition the anodic dissolution at crack tip was the dominant mechanism. While at high pH medium, the hydrogen based mechanism was dominant.

Self-Assembly Behavior of Amphiphilic Poly(amidoamine) Dendrimers with a Shell of Aniline Pentamer

A series of amphiphilic poly(amidoamine) dendrimers (PAMAM, G2-G5) composed of a hydrophilic core and a hydrophobic shell of aniline pentamer (AP) were synthesized and characterized. The modified dendrimers self-assembled to vesicular aggregates in water with the critical aggregation concentration (CAC) decreased in the order of G2 > G3 > G4 > G5. It was found that the modified dendrimers self-organized into spherical aggregates with a bilayer vesicular structures and that the dendrimers in higher generation have more order structure, which may be attributed to the crystallization induced by the compacted effect of AP segments. In addition, larger spherical vesicles were observed under acidic and alkaline conditions, as compared with sizes of aggregates in neutral medium. At low pH, the tertiary amine groups of PAMAM-AP were transformed to ammonium salts; the polarons were formed from AP units by doping with strong acids, thereby leading to the stability of vesicular aggregates being better than that in double distilled water. Nevertheless, in high pH environment, the deprotonation of PAMAM-AP caused the enhancement of π-π interactions, resulting in generation of twins or multilayered vesicles.

EphB–EphrinB Interaction Controls Odontogenic/Osteogenic Differentiation with Calcium Hydroxide

IntroductionCalcium hydroxide is used in direct pulp capping of uncontaminated exposed vital pulps caused by mechanical or traumatic injury. Calcium hydroxide creates a high alkaline pH environment and initiates a mineralized tissue formation in the pulp. The exact mechanism by which calcium hydroxide induces the reparative dentin formation is unknown. Because Eph receptors and ephrin ligands play a role in pulp stem cell migration and proliferation, our hypothesis is that calcium hydroxide–related odontogenic/osteogenic differentiation may be associated with Eph-ephrin interaction. The aim of this study was to investigate whether Eph-ephrin interaction regulates odontogenic/osteogenic differentiation with calcium hydroxide. MethodsPrimary pulp cells were harvested from the molars of C57BL/6 mice. The cells were treated with calcium hydroxide. Immunofluorescence was used to detect protein expression. A knockout of the ephrinB1 or EphB2 gene was performed with short hairpin RNAs. Cell migration, proliferation, and gene expression were then analyzed. ResultsCalcium hydroxide stimulated EphB2 gene expression but suppressed ephrinB1 gene expression at the proliferation stage. However, calcium hydroxide stimulated both ephrinB1 and EphB2 gene expression at the differentiation stage. In addition, EphB2 localized at ephrinB1–positive cells at the area of Dentin sialoprotein (DSP) staining, which increased with calcium hydroxide treatment. Knockdown of ephrinB1–EphB2 significantly suppressed cell proliferation. Additionally, knockdown of the ephrinB1 gene caused cell migration, whereas a lack of the EphB2 gene suppressed calcium hydroxide–induced mineralization from primary pulp cells. ConclusionsEphrinB1–EphB2 interaction contributes to calcium hydroxide–induced odontogenic/osteogenic differentiation. This observation is the first finding of the mechanism of calcium hydroxide–induced odontogenic/osteogenic differentiation.

Investigating humic substances interactions with Th4+, [formula omitted], and [formula omitted] at high pH: Relevance to cementitious disposal of radioactive wastes

A number of geodisposal concepts for intermediate level radioactive waste involve geological emplacement within cementitious repositories. Such facilities, once rehydrated with groundwater, will create high pH environments due to aqueous phase reaction of the cements. This work focuses on the interactions of several important long-lived radionuclide cations with dissolved organic matter (DOM) constituents (humic and fulvic acids) under high pH conditions. We also sought to test the comprehensive speciation model WHAM/Humic Ion Binding Model VII for these specific conditions. Results for Th demonstrate high fractions present as organic complexes at all pH values. Binding of neptunyl to DOM shows a maximum over the pH range expected within an evolving repository. Uranyl exhibits decreasing binding with pH, however, the majority of metal in solution is present as organic complexes under the lower pH conditions investigated (10–10.5). We have updated the WHAM/Model VII binding values for UO22+, and have for the first time added NpO2+ values to the database. These updates now allow application of the model for more complex mixtures across the entire repository pH range. Calculations for three simulated cement interstitial waters (representing different degradation phases) suggest U(VI) and Np(V) are not likely to be significantly bound to DOM under these conditions.

Influence of carbon on stress corrosion cracking of high strength pipeline steel

To understand the influence of carbon on stress corrosion cracking of pipeline steels, a carburization treatment was applied to API X80 steel. Carbon-rich structures rather than ferrite grains remain intact and act as cathode during immersion in the acidic environment. Coalescence of micro-cracks induced by galvanic effect and higher dissolution inclination of ferrite grains lead to the higher driving force for crack growth within grains in the low pH environment. Higher average crack velocity at grain boundaries and passivation of ferrite grains provide higher driving force for crack propagates along grain boundaries in the high pH environment.

Halomonas johnsoniae: Review of a Medically Underappreciated Genus of Growing Human Importance

The growing genus Halomonas includes bacteria favoring or tolerating high-saline/halide and high-pH environments. Infections are rarely reported. A patient developed Halomonas johnsoniae (previously reported only as dialysis unit environmental contaminants) bacteremia. The medical community is alerted to the pathogenic potential of the genus, particularly in a dialysis setting.

Corrosion of Aluminized Steel in Aggressive Natural Water

Aluminized steel Type 2 (AST2) has a ~50 µm thick coating with outer and inner layers of mostly Al and Fe-Al intermetallic respectively. AST2 is used for culvert and drainage pipes that are required to have long service life. The use of calcium carbonate-rich backfill (limestone) found to be a key contributing factor to the observed early deterioration. Limestone contributed to form a high pH environment sufficient to cause passivity breakdown of the passive film on aluminum. AST2 specimens were exposed in limestone-water cells with water being continuously replenished at a slow rate. A high steady state pH developed that was aggressive to aluminum passive film. Electrochemical measurements and direct inspection indicated onset of severe early corrosion with consequent fast wastage of the outer film. Corrosion rate decreased later as a thick corrosion product layer covered the surface and formed a transport limitation barrier.

Microbial Reduction of Fe(III) under Alkaline Conditions Relevant to Geological Disposal

To determine whether biologically mediated Fe(III) reduction is possible under alkaline conditions in systems of relevance to geological disposal of radioactive wastes, a series of microcosm experiments was set up using hyperalkaline sediments (pH ~11.8) surrounding a legacy lime working site in Buxton, United Kingdom. The microcosms were incubated for 28 days and held at pH 10. There was clear evidence for anoxic microbial activity, with consumption of lactate (added as an electron donor) concomitant with the reduction of Fe(III) as ferrihydrite (added as the electron acceptor). The products of microbial Fe(III) reduction were black and magnetic, and a range of analyses, including X-ray diffraction, transmission electron microscopy, X-ray absorption spectroscopy, and X-ray magnetic circular dichroism confirmed the extensive formation of biomagnetite in this system. The addition of soluble exogenous and endogenous electron shuttles such as the humic analogue anthraquinone-2,6-disulfonate and riboflavin increased both the initial rate and the final extent of Fe(III) reduction in comparison to the nonamended experiments. In addition, a soluble humic acid (Aldrich) also increased both the rate and the extent of Fe(III) reduction. These results show that microbial Fe(III) reduction can occur in conditions relevant to a geological disposal facility containing cement-based wasteforms that has evolved into a high pH environment over prolonged periods of time (>100,000 years). The potential impact of such processes on the biogeochemistry of a geological disposal facility is discussed, including possible coupling to the redox conditions and solubility of key radionuclides.

Caustic stable anion-exchange membranes for EDR applications in municipal and industrial wastewater recovery: piloting and field investigations

GE membrane based Electrodialysis Reversal (EDR) systems offer attractive characteristics such as higher water recovery, increased resistance to scaling and fouling, and membrane stability in oxidative environments. Research activity at GE Water & Process Technologies, have extended these capabilities to include high pH environments, through the development of a new high performance anion exchange membrane that tolerates aggressive caustic cleaning conditions. This will enable the expanded application of EDR systems in markets that are limited by the currently practiced cleaning-in-place procedures.

Site selectivity for protein tyrosine nitration: insights from features of structure and topological network

Tyrosine nitration is a covalent post-translational modification, which regulates protein functions such as hindering tyrosine phosphorylation and affecting essential signal transductions in cells. Based on up-to-date proteomics data, tyrosine nitration appears to be a highly selective process since not all tyrosine residues in proteins or all proteins are nitrated in vivo. Quite a few investigations included the protein structural information from the RCSB PDB database, where near 100,000 high-quality three-dimensional structures are available. In this work, we analyzed the local protein structures and amino acid topological networks of the nitrated and non-nitrated tyrosine sites in nitrated proteins, including neighboring atomic distribution, amino acid pair (AAP) and amino acid triangle (AAT). It has been found that aromatic and aliphatic residues, particularly with large volume, aromatic, aliphatic, or acidic side chains, are disfavored for the nitration. After integrating these structural features and topological network features with traditional sequence features, the predictive model achieves a sensitivity of 63.30% and a specificity of 92.24%, resulting in a much better accuracy compared to the previous models with only protein sequence information. Our investigation implies that the site selectivity may stem from a more open, hydrophilic and high-pH chemical environment around the tyrosine residue.

Electroactivity of Polyaniline in High pH Solutions

Generally, the redox activity of polyaniline (PANI) can only be retained in acidic media at pH<4, because the occurrence of deprotonation of the nitrogen atoms in the PANI backbone at high pH values may result in the loss of conduc- tivity and electroactivity in neutral or alkaline solutions. This high acidity requirement greatly limits its potential applications like biosensor, marine antifouling and anticorrosion, where neutral or alkaline environments must be faced. Much effort has been exerted in the development of approaches to overcome this issue. In summary, two principal strategies have been pro- posed to shift the electroactivity of PANI to a high pH environment. One is based on a mechanism of protonic acid doping, the other is based on a charge transfer process. The former is to introduce acidic groups into the PANI chains or PANI sys- tems to hinder the deprotonation of its conducting form and thus to preserve its electroactivity at higher pH values. The main approaches to introduction of acidic groups include the sulfonation of the emeraldine base of PANI, the homopolymerization of aniline derivatives with acidic ionogenic groups or the copolymerization of aniline and aniline derivatives, and the forma- tion of PANI complexes by doping with macromolecular acids. The latter is to use a hybrid film fabricated by incorporating conductive nanomaterials into a PANI matrix, which can improve the charge transfer rate across the PANI matrix and facili- tate its redox processes. The development of PANI nanocomposites prepared by doping with carbon nanotubes, graphenes and Au nanoparticles, etc., falls into this category. This review article provides an overview of various approaches to preserve the electroactivity of PANI in high pH solutions on the basis of the two main strategies. Special emphasis is placed on the synthetic methods and electrochemical features for the self-doped, polymer acid-doped and CNT-doped PANIs, including their underlying mechanisms for achieving good electroactivity. The main challenges and future research directions in this field are also discussed. Keywords polyaniline; electroactivity; high pH values; protonic acid doping; charge transfer

In Vitro Release Evaluation of Gastroretentive Amoxicillin Floating Tablets Employing a Specific Design of the Flow-Through Cell

Floating amoxicillin trihydrate (AmoxT) tablets, used for eradication of Helicobacter pylori (H. pylori), were prepared according to a gas-generating technique to extend the drug residence time in the stomach. The drug release rate from the floating tablets in acidic dissolution medium, in which AmoxT is known to be unstable, was studied using two dissolution techniques: openloop system of the flow-through cell (FTC) and the beaker method. Analysis of AmoxT in the dissolution medium was carried out by UV spectrophotometric and HPLC methods. The comparison indicates that the open-loop system of the FTC, which is based on non-cumulative (fresh) dissolution samples, is the preferred dissolution technique, and in this case, the drug could be analyzed by UV spectrophotometric and HPLC methods. However, in the case of a large number of QC samples, UV spectrophotometry is preferred to the HPLC method, which requires relatively longer time for analysis thereby increasing drug degradation. On the other hand, in the case of the beaker method, which is based on cumulative dissolution samples, the drug must be analyzed by HPLC. Generally, the beaker method is not recommended due to the problems associated with the accumulation of AmoxT degradation product in the dissolution medium. This study describes a simple dissolution method capable of discriminating between different AmoxT gastroretentive formulations without any additional experimental or calculational steps. INTRODUCTION The lifetime risk for developing a peptic ulcer is approximately 10% of the general population (1, 2). H.pylori is one of the major causative agents of peptic ulcer (1). Although many antibacterial agents have a very low minimum inhibitory concentration (MIC) against H.pylori in vitro (3), no single agent is effective in the eradication of the infection in vivo when administered alone (4). In addition, single antibiotic therapy is strongly discouraged to prevent the development of resistant strains (5). There could be one or several reasons for the failure of single-antibiotic therapy against H.pylori. Firstly, the organism resides in the mucus gel close to the acidic environment of the gastric fluid. Many antibacterial agents, such as penicillin and erythromycin, degrade rapidly in acidic medium. Secondly, the drug must diffuse into the mucus layer to furnish concentrations sufficient for antibacterial activity. Lastly, the contact time of antibacterial drugs with the organism needs to be sufficiently long for successful eradication of H.pylori from the gastric mucosa (6), which can be achieved through a gastroretentive drug delivery system (GRDDS). Gastric residence time of an oral dosage form is affected by several factors. To pass through the pyloric valve into the small intestine, the particle size should be in the range of 1–2 mm (7, 8). The rate of gastric emptying depends mainly on viscosity, volume, and caloric content of meals. The nutritive density of meals helps to determine gastric emptying time. It does not make any difference whether the meal has high protein, fat, or carbohydrate content as long as the caloric content is the same. However, an increase in acidity and caloric value slows down gastric emptying time. Biological factors such as age, body mass index (BMI), gender, posture, and diseased states (diabetes, Crohn’s disease) influence gastric emptying. In the case of elderly people, gastric emptying is slowed down. Generally, females have slower gastric emptying rates than males. Stress increases gastric emptying rates while depression slows it down (7, 9, 10). Different drug delivery methods can be used for gastric retention such as floating (11), mucoadhesive, superporous hydrogel, expandable, magnetic, and high-density systems (12). GRDDS is superior for (1) drugs that are locally active in the stomach (e.g., misroprostol, antacids); (2) drugs that have narrow absorption windows in the gastrointestinal tract (GIT) (e.g., L-DOPA, para aminobenzoic acid, furosemide, riboflavin); (3) drugs that are unstable in the intestinal or colonic environment (e.g., captopril, ranitidine HCl, metronidazole); (4) drugs that disturb normal colonic microbes (e.g., antibiotics against H. pylori); and (5) drugs that exhibit low solubility at high pH values (e.g., diazepam, chlordiazepoxide, verapamil HCl) (13). In practice, drugs that are less soluble in a high pH environment require more retention time in the stomach to improve *Corresponding author. e-mail: ashmawya@yahoo.com dx.doi.org/10.14227/DT200113P27

Application of DGT to high pH environments: uptake efficiency of radionuclides of different oxidation states onto Chelex binding gel

The DGT Chelex binding phase has not been tested for binding efficiency over the extreme high pH range (i.e., 10 to 13). Here, we examined the uptake efficiency of the gel-encapsulated Chelex cation exchange resin binding phase when in direct contact with solutions of radionuclides of different oxidation states over the circumneutral to high pH range (∼7 to 13). Results show that the Chelex binding gel is suitable for Eu(3+) for circumneutral pH, for UO2(2+) up to at least pH 10.7 and for NpO2(+) up to at least pH 11.7. Application may be appropriate at higher pH values but testing of complete solution deployment units will be required. This work provides the framework to use DGT as a tool for the study of high pH radionuclide systems.

Surface Tests to Demonstrate the Construction Feasibility of the Belgian Supercontainer

The Supercontainer (SC) is a reference concept, adopted by the Belgian Agency for Radioactive Waste and Enriched Fissile Materials (ONDRAF/NIRAS), for the packaging of high level vitrified radioactive waste (HLW) and spent fuel (SF). The waste package consists of different components all designed to fulfil specific functions. One of these is a carbon steel overpack developed to prevent contact of the waste with the engineered barrier system and the host geological formation during the thermal phase. Another is a concrete buffer and cementitious filler, both developed to provide a high pH environment during at least the thermal phase, which ensures passivation of the overpack and provides radiological shielding during construction and handling of the SC. Finally, the presence of an outer steel envelope serves as a mould for the casting of the outer buffer while providing additional mechanical strength and confinement during transportation and handling of the waste package. As part of the first safety and feasibility case (SFC-1), ONDRAF/NIRAS has to demonstrate that no fundamental flaws exist regarding the feasibility to construct the SC. To this end, ONDRAF/NIRAS established a research programme consisting of desk studies, modelling, theoretical development and experimental testing. The primary objective of the experimental testing programme is to demonstrate the feasibility to construct the SC. This paper describes the test's setup and design and provides a summary of the main observations obtained during an experimental test performed to evaluate the construction feasibility of the SC.

Hydroxide ion flux and pH-gradient driven ester hydrolysis in polymer vesicle reactors

In this article, we measured the hydroxide ion flux across poly(ethylene oxide-b-butadiene) (PEO-PBD) membranes, and characterized the magnitude of established pH gradients. In terms of permeability, PEO-PBD vesicles (polymersomes) are suitable polymeric analogues of lipid vesicles, with comparable permeabilities that can be tuned by varying the molecular weight (i.e. membrane thickness) of the polymer amphiphiles. PEO-PBD dispersions were found to be capable of maintaining gradients of up to 6 pH units for several weeks and their utility for partitioning acid-ionisable species inside polymer vesicles was demonstrated. Furthermore, pH gradients across vesicle membranes can be used to drive spatially-confined chemical reactions, and these gradients were used to facilitate the reaction of a fluorogenic compound, fluorescein diacetate, inside the high pH environment confined to the polymersome interior. In this sense, pH-gradient vesicles can act as artificial lysosomes, facilitating the collection and digestion of materials that can be hydrolysed in alkaline environments.

Dissolution of vitrified wastes in a high-pH calcium-rich solution

The current baseline for the conditioning of most UK intermediate-level radioactive waste (ILW) is immobilisation using cement. However, vitrification of some UK ILW is being considered as an alternative. One option for the disposal of the resulting vitrified ILW would be to place it in a geological disposal facility in a high-pH environment with cemented ILW and a cement-based backfill. Therefore, the potential effects of such a high pH (∼12.5), calcium-rich cement-based environment on the dissolution behaviour of simulant ILW glasses have been studied using the product consistency test (PCT). Three non-radioactive waste compositions were assessed: a laboratory simulant ILW vitrified in a borosilicate glass and two full-scale simulant vitrified products (a slag containing simulant plutonium-contaminated material and Magnox sludge; and a glass containing clinoptilolite). Powdered samples were leached in saturated Ca(OH)2 solutions for up to 42days at temperatures between 30 and 90°C.In general the rates of dissolution were lower than expected at such a high pH compared to studies in the literature under alkaline conditions. In contrast to the typical dissolution behaviour of high level waste (HLW) glasses, dissolution of the simulant borosilicate ILW glass was initially slow, followed by a period of faster boron and alkali metal release. The saturation/residual regime was not reached within experimental timescales. The rate of dissolution during the period of faster release increased with increasing temperature; the activation energy for this stage of dissolution was calculated to be 47±2kJmol−1 based on boron release. The two full-scale simulant glasses, which contained negligible boric oxide, exhibited conventional static dissolution profiles, and entered the residual rate regime after 7-14days at 50°C. The greater durability of the full-scale simulants is thought to be due to the greater content of network-forming oxides in these glasses compared to the borosilicate glass. It is also suggested that the formation of calcium borates may delay initial hydration of the borosilicate glass in a similar manner to the retardation of cement hydration by soluble borates. More generally, the formation of calcium- and magnesium-containing precipitates on the surface of the vitrified wastes, and agglomeration of the powder, appeared to act to reduce the dissolution rate. Overall these results suggest that calcium has an important role in the long-term durability of vitrified wastes at high pH.

Backbone stability of quaternized polyaromatics for alkaline membrane fuel cells

The backbone stability of benzyl-trimethyl ammonium (BTMA) functionalized polyaromatics was investigated in two structurally differing polymer architectures; quaternized poly(arylene ether) (PAE) and poly(phenylene) (PP). FTIR analysis indicated the cleavage of aryl-ether linkages in quaternized PAEs under high pH environments, while no backbone degradation in quaternized PP was observed. The backbone degradation of PAEs not only significantly reduced the mechanical properties of the membranes, but also negatively impacted hydroxide conductivity. Membrane electrode assemblies (MEAs) using both PAE and PP membranes showed good initial alkaline membrane fuel cell performance. However, the PAE MEA displayed larger performance losses and failure after only 55h, due to a mechanical breach. No catastrophic failure of the PP MEA occurred after 300h, which further confirmed the stability of the polymer backbone.