Enhanced hydroxide ion conductivity of imidazolium functionalized poly (ether ether ketone) membrane by incorporating N,N,N′,N′-tetramethyl-1,4-phenylenediamine

Anion-exchange membranes (AEM) are prepared from chloromethylated poly(ether ether ketone) (CMPEEK), which is quaternized by N,N,N′,N′-tetramethyl-1,4-phenylenediamine (TMPD) and 1-methylimidazole using a two-step method. TMPD can not only improve the mechanical properties but also provide more ion exchange groups and improve the availability of quaternary ammonium (QA) groups. By varying the amount of TMPD in the membrane casting solution, the comprehensive properties of the membranes are optimized and intensified. The anion conductivity is increased from 0.028 S cm−1 of the imidazolium functionalized poly (ether ether ketone) (ImPEEK) control membrane to 0.042 S cm−1 of the TMPD/ImPEEK membrane with a TMPD content of 5 wt%. Meanwhile, a 31.5% increase in ultimate tensile strength and a 27.8% increase in Young's modulus of the TMPD/ImPEEK membrane are achieved. This study exploited a facile approach to solving the trade-off relation between anion conductivity and mechanical properties.