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A series of tertiary amine and siloxane crosslinked composite anion exchange membranes were prepared by incorporating 2‐(3,4‐epoxycyclohexyl) ethyltrimethoxysilane (EHTMS) and N,N,N′,N′‐Tetramethyl‐1,6‐hexanediamine (TMHDA) into N‐Methyldiethanolamine (MDEA)‐functionalized poly (2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) backbone via sol‐gel process. The resultant membranes named as AEM‐X (X = 1, 2, 3, 4), which own a three‐dimensional (3D) cross‐linking structure, exhibit superior swelling resistance, mechanical properties, even the thermal stability is up to 220°C. Compared with AEM‐1 (contains no crosslinker), the swelling ratio of AEM‐2 obviously decreases by 10.2% at 80°C, while the OH− conductivity of AEM‐2 has a merely 1.9% decline (20.6 mS cm−1) at 80°C and can maintain 67% of its initial value in a 2 M aqueous NaOH at 80°C for 240 h. The simultaneous introduction of inorganic siloxane and organic linear crosslinker provides a new idea for the preparation of anion exchange membranes with largely improvement in dimensional stability and alkali resistance while the ionic conductivity is kept at comparatively high level.

A series of alkaline anion exchange membranes (AAEMs) based on poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) with multi‐cation side chain containing piperidinium group were fabricated via nucleophilic substitution and Menshutkin reaction. The chemical structures of the AAEMs (PPO‐AMP‐X) were determined by Fourier transform infrared and proton nuclear magnetic resonance spectra. The resultant PPO‐AMP‐X membranes with the ion exchange capacities (IECs) of 2.05–2.77 mmol g−1 displayed the hydroxide conductivities in the range of 61.04–78.92 mS cm−1 at 80°C. When tested at the same degree of functionalization levels, the PPO‐AMP‐X membranes exhibited significantly higher hydroxide conductivity and lower conductivity loss than conventional AAEMs bearing benzyltri‐methylammonium group (PPO‐TMA). The PPO‐AMP‐28 multi‐cation membrane showed a hydroxide conductivity of 70.52 mS cm−1 at 80°C, which was nearly two times higher than that of the PPO‐TMA‐28 single‐cation membrane (36.74 mS cm−1). Compared with PPO‐TMA‐28 (56.76% decrease), the hydroxide conductivity of PPO‐AMP‐28 merely decreased by 23.15% after soaked in 1 M KOH at 80°C for 500 h. Additionally, the PPO‐AMP‐X membranes displayed moderate mechanical properties and good thermal stabilities, which can meet the basic requirements for use in fuel cells. This study provides a facile method for preparing AAEMs with multi‐cation side chain containing piperidinium group.

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