Modification of poly(aryl ether ketone) using imidazolium groups as both pendants and bridging joints for anion exchange membranes

Quaternary imidazolium groups were grafted onto poly(aryl ether ketone) as both pendants and joints of crosslinking by using 1-methylimidazole and C2-substituted imidazole of 2-undecylimidazole in a certain mole ratio. Crosslinking of the imidazolium-functionalized poly(aryl ether ketone) was performed with three dibromoalkane crosslinkers having different alkyl chain-length in order to know the correlation of the structure and property of the crosslinked membranes meanwhile to enhance their mechanical strength. The obtained crosslinked membranes in hydroxide form showed a high tensile strength of about 20 MPa at room temperature with less swelling, and they were thermally stable up to around 230 degrees C according to the data of thermogravimetric analysis. All the crosslinked anion exchange membranes exhibited conductivities in purified water of higher than 0.010 S cm(-1) at 25 degrees C, and over 0.040 S cm(-1) at 80 degrees C, respectively. The durability of the membranes in alkaline medium was tested by monitoring the changes in conductivity, ion exchange capacity (IEC) and tensile strength at break, respectively. The results indicate that the anion exchange membrane crosslinked with a long alkyl spacer demonstrated high tolerance to the nucleophilic attack. In addition, the increase in the temperature could accelerate the degradation of the polymer membrane more than that increase in the concentration of the alkaline solution. (C) 2015 Elsevier Ltd. All rights reserved.