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• PECH-based polyelectrolytes of different architectures were synthesized. • PECH undergoes chain scissions and dehydrochlorination reactions in alkaline medium. • Degradation reactions are favored by a high concentration of KOH electrolyte. • PECH crosslinking via DABCO limites both KOH uptake and degradation reactions. • A high crosslinked membrane is stable even it contains a high cationic sites amount. The chemical stability of anion exchange membranes (AEM) is crucial for the durability of the electrochemical devicesusing them. In this context, poly(epichlorohydrin)-based AEM were subjected to chemical degradation in the presence of a corrosive alkaline medium. Linear and cross-linked polyelectrolytes grafted with ammonium cations based on Quinuclidine and/or DABCO were first synthesized. They were characterized by an IEC comprising between 1.3 and 3.1 mmol/g, an ionic conductivity above 2 mS/cm and transport numbers between 0.71 and 0.89. Their chemical stability was then evaluated after immersion in 1 M to 8 M KOH solutions for 672 h at 50 °C. The evolutions of these characteristics as well as the molecular structure of the materials during this period inform on the chemical resistance of the polymer backbone as well as that of the cationic sites. The main degradation reactions have been identified as chains scission and Hofmann elimination, leading to the loss of the cationic groups. Nevertheless, these reactions can be limited by a high crosslinking density of the membrane, enhancing then its chemical stability despite a high ammonium group content. [ABSTRACT FROM AUTHOR]

Aqueous alkaline metal-air batteries represent promising energy storage devices when supplied with atmospheric air. However, under this condition, the air electrode shows a very short life time (i.e. 50 h of operation in 5 M LiOH at −10 mA cm −2 ), mainly due to the precipitation of carbonates inside the electrode porosity. The air electrode can then be protected by an anion exchange membrane on the electrolyte side. In this paper, we demonstrate that the efficiency of this protective membrane depends on the assembly method on the electrode. When a modified poly(epichlorohydrin) (PECH) network is synthesized directly on the electrode, the polymer seeps inside the electrode porosity, and a suitable interface inducing negligible additional polarization in comparison with classical pressure-assembled membranes is obtained. This protected electrode shows improved stability of up to 160 h of operation in 5 M LiOH. This performance is improved to 350 h by adjusting the conductivity and the ionic exchange capacity. Finally, the interest of interpenetrating polymer network (IPN) architecture compared to a single network is confirmed. Indeed, an electrode protected with a PECH/poly(2-hydroxyethyl methacrylate) (PHEMA) IPN is stable for 650 h in 5 M LiOH. In addition, degradation process becomes reversible since the assembly can be regenerated, which is not possible for the bare electrode. [ABSTRACT FROM AUTHOR]

Abstract: Original membranes based on an interpenetrating polymer network (IPN) architecture combining a poly(2-acrylamido-2-methyl-1-propane sulfonic acid) (AMPS) network and a fluorinated network were synthesized. The AMPS weight compositions were varied from 50 to 70wt%. The first network was achieved by radical copolymerization of AMPS with a fluorinated telechelic diacrylate while the second one was obtained by photoinitiated cationic copolymerization of telechelic fluorinated diepoxide with trimethylol propane triglycidyl ether. The morphologies of these different IPNs were deduced from small-angle X-ray scattering (SAXS) spectra and dynamic thermomechanical analysis (DMTA). The main functional properties related to their use as proton exchange membrane in fuel cells were quantified, such as water vapor sorption, liquid water uptake (22–59wt%), proton conductivity (1–63mS/cm), gas permeability (0.06 and 0.80 barrer for dry oxygen and hydrogen, respectively), and oxidative and thermal stabilities. More precisely, the effects of the ionic exchange capacity (IEC) varying from 1.73 to 2.43meq/g and the cross-linking density of the conducting phase on the morphology and the properties of IPN membranes were studied in detail. Finally, these IPN membranes were tested as fuel cell membrane and a correlation between the ex-situ and in-situ characterizations was established. [Copyright &y& Elsevier]