Effect of hydrophobic butyl group on the physicochemical properties of anion exchange membranes based on pyperazinum functionalized polyketone copolymer

In this report, anion exchange membranes based on poly[(N-(1,4-dimethyl piperaziniumethyl)-ethylenepyrrole)(X)/ethyleneketone/propyleneketone/N-(n-butyl)ethylenepyrrole], where X = I− or OH−, terpolymer are prepared by converting the 1,4-diketonic groups of an aliphatic poly[ethylene ketone/propylene ketone] (PKK) into pyrrole substituted repeat units through a Paal-Knorr reaction. These materials are prepared by co-reacting 1-(2-aminoethylpiperazine) and n-butylamine in different amines/PKK molar ratios to investigate the effect of varying degree of functionalization (f) and the incorporation of hydrophobic butyl pendant groups on the physicochemical properties of the membranes. The molecular structure and composition of the membranes are confirmed by ATR-FTIR and CHNS/O elemental analysis, while their electrochemical and physical properties are characterized through evaluation of water uptake (WU %), ion exchange capacity (IEC), thermal stability, ionic conductivity, and alkaline stability. BES studies reveal ionic conductivity values of 0.49 and 0.87 mS cm−1 at 50 °C for the membranes in iodide and hydroxide form, respectively. The membrane PB-FPKK0.47/0.04(OH)0.43 demonstrates an exceptional chemical stability for 720 hours at 45 °C in 1 M KOH aqueous solution.