Synergy effects of hindered phenol and diphosphite antioxidants on promoting alkali resistance of quaternary ammonium functionalized poly(4-vinylbenzyl chloride-styrene) anion exchange membranes

Recent Advances in the Synthesis of Commercially Available Phosphite Antioxidants

Phosphite antioxidants exhibit superior anti-aging and color-stabilizing properties when incorporated into polymer materials. Their synergistic antioxidative effects are particularly noteworthy when used in combination with hindered phenol antioxidants and other primary antioxidants, serving as effective secondary antioxidants, displaying noteworthy synergistic antioxidation effects. This review systematically classifies the synthetic methods for phosphite antioxidants into three distinct categories based on the types of starting materials: synthesis from phosphorus trichloride, phosphorus-containing esters, and white phosphorus. Additionally, it delineates the reaction mechanisms associated with these approaches and provides an overview of future potential research directions and applications for organophosphorus antioxidants.

On the Radical-Induced Degradation of Quaternary Ammonium Cations for Anion-Exchange Membrane Fuel Cells and Electrolyzers

Four benzylic-type quaternary ammonium (QA) compounds with different electron density at the phenyl group were evaluated for their susceptibility against degradation by radicals. Time-resolved absorption spectroscopy indicated that radicals with oxidizing and reducing character were formed upon oxidation by HO⋅ and O⋅- (conjugate base of HO⋅). It was estimated that, dependent on the QA, 18-41 % of the formed radicals were oxidizing with standard electrode potentials (E0 ) above 0.276 V and 13-23 % exceeded 0.68 V, while 13-48 % were reducing with E0 <-0.448 V. The stability of these model compounds against oxidation and reductive dealkylation was evaluated at both neutral and strongly alkaline conditions, pH 14. Under both conditions, electron-donating groups promoted radical degradation, while electron-withdrawing ones increased stability. Therefore, durability against radical-induced degradation shows an opposite trend to alkaline stability and needs to be considered during the rational design of novel anion-exchange membranes for fuel cells and electrolyzers.

New block poly(ether sulfone) based anion exchange membranes with rigid side-chains and high-density quaternary ammonium groups for fuel cell application

We report a series of novel poly(ether sulfone) based anion exchange membranes (AEMs) with relatively good stability due to their rigid side-chains and heterocyclic quaternary ammonium groups. The AEMs show appropriate performance in AEM fuel cells.