The Effect of Micro-Morphology on Alkaline Polymer Electrolytes Stability.

Recent studies demonstrated that the chemical stability of alkaline polymer electrolytes (APEs) could be improved by reducing the inductive effect between cations and backbones. Therefore, pendent cations were recommended. However, micro-phase separated morphologies would be generated by elongating the spacer between cations and backbones, which have a significant influence on the chemical stability of APEs too. In order to analyze how the patterns of micro-morphology affect the chemical stability of the materials, in the present work, four APEs ( a-QAPS, a-QAPS, a-QAPS and a-QAPS) with different lengths of side chain between polysulfone and quaternary ammonium are synthesized. The longer of the side chain is, the more obvious of the micro-phase separation for the a-QAPS membranes is observed. After immersing in a hot alkaline solution (80 °C, 1 M KOH) for 30 days, a-QAPS exhibits the highest chemical stability. The IEC and ionic conductivity of a-QAPS film are reduced by 10.0% and 10.5%, respectively. The weight loss of a-QAPS membrane is 8.0%, which is similar with the value of the pristine backbone. The increased chemical stability can be ascribed to the suitable micro-morphology constructed in a-QAPS sample. Besides, a-QAPS membrane shows a high conductivity of 75.5 mS cm, while the swelling ratio is limited to 15.0% in liquid water at 80 °C. And a peak power density of 339.1 mW cm is obtained by applying a-QAPS as the APE to the H-O fuel cell at 60 °C.