Preparation and characterization of high conductivity comb polymer anion exchange membranes

A comb-shaped anion exchange membrane was successfully constructed by simultaneously introducing a hydrophobic aliphatic long-chain bromododecane (BA) and a hydrophilic short-chain bromoethanol (BE) as a quaternizing agent into the side chain of poly-4-vinyl-pyridine (P4VP). The aforementioned membrane chemical structure was investigated by FT-IR, and confirmed that the BA and BE were successfully grafted onto the P4VP backbone. A series of performance test results reveal that the water uptake (WU) and swelling ratio (SR) are effectively controlled with the BA content increased from 0% to 75.0%, which the value was corresponding to the water uptake decreases from 92.3% to 31.8%, and the swelling ratio decreases from 78.4% to 7.8%. Interestingly, the conductivity of synthesized membrane in this paper is much increased with substantially the same ion exchange capacity (IEC) (from 50.0 mS.cm(-1) for BE100.0%-BA(0%)/P4VP to 75.0 mS.cm(-1) for BE25.0%-BA(75.0%)/P4VP at 70 degrees C), which can be attributed to the microphase-separated structure. On the other hand, the membrane BE25.0%-BA(75.0%)/P4VP has the best overall performance, which with the conductivity of 75.0 mS.cm(-1) at 70 degrees C, which the temperature closest to the alkaline fuel cell operating temperature. And it also had excellent tensile strength (16.0 MPa) and elongation at break (5.9%), indicating sufficient flexibility and processability, and it has excellent chemical stability immersed it into 3 mol.L-1 KOH for up to 240 h, which was the conductivity can still reach more than 70% of the initial value. And the aforementioned membrane also with the better thermal stability (the thermal decomposition temperatures above 200 degrees C). The single cell test result reveal that the membrane displayed good cell performance with a power density of 47.52 mW.cm(-2) at 70 degrees C. In summary, the comprehensive performance of BE25.0%-BA(75.0%)/P4VP is expected to be applied to alkaline polymer fuel cells.