A novel cross-linked anion exchange membrane with conjugated and non-conjugated pyridine groups

A novel cross-linked pyridine anion exchange membrane was synthesized via thermal cross-linking methods. 2,5-bis(2,3,4,5,6-pentafluorophenyl)-1,3,4-oxadiazole (FPOx) and diallyl bisphenol A (DABPA) were reacted to obtain the main polymer chain (MP). MP was substituted with 4-bromopyridine and 4-hydroxypyridine to generate two pyridine polymers conjugated pyridine polymer (CPP) and non-conjugated pyridine polymer (NPP). The different conjugation statues of CPP and NPP led to distinct mechanical and electrochemical properties. The diallyl groups in MP acted as the cross-linking structures which strengthened the mechanical properties of CPP and NPP and provided more flexible side chains. The ultimate membrane CPP-membrane and NPP-membrane were prepared by solution casting methods. Compared with NPP-membrane, the ionic conductivity of CPP can achieve to 20.1 mS/cm at 20 °C with excellent mechanical and thermal characteristics. Quantum theory computation and AFM morphology were carried out to figure out the reason of the difference in ionic conductivities and physical properties.