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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.

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Aliphatic polymers, such as polypropylene, styrene ethylene butylene styrene and norbornene, which show great alkaline stability and flexibility, have become the main research trend of the skeleton of anion exchange membranes. Here, we prepared a copolymer with all carbon atoms on the main chain. Firstly, a new vinylimidazole cationic monomer was prepared, and then copolymerized with styrene and acrylonitrile to obtain a copolymer (PASIm). Furthermore, (2,6-dimethyl-1,4-phenylene oxide) (PPO) was introduced to cross-link with PSAIm to prepare AEMs with different crosslinking degrees (CEM-X, X = 6,12,18,24,30). 1H NMR and FT-IR showed that PASIm was successfully synthesized and crosslinked with PPO. The prepared membranes had high hydroxide ionic conductivity and excellent alkaline stability. AFM showed that the CEM-18 had obvious microphase separation structure, which was beneficial to the construction of ion channels in the membrane. Thus, the CEM-18 showed the highest ionic conductivity, up to 59.21 mS cm−1 at 80 °C. CEM-24 with higher crosslinking degree showed the highest alkaline stability. After immersing in 1 M KOH solution at 80 °C for 240 h, 86.52% of the initial ionic conductivity was retained. These results indicate that the prepared anion exchange membranes have broad application prospects.