In order to show the impact of the molecular weight (MW) of poly(2,5-benzimidazole) (ABPBI) on its physicochemical properties, a series of ABPBI polymers with different MWs ranging from 20 to 113 kDa were synthesized and fabricated into conductive films. The ABPBI films are characterized by different spectroscopic methods measuring the acid loading level, acid retention capability, ion exchange capacity (IEC), and the proton conductivity. Notably, the phosphoric acid (PA) loading ratio increased with the increase of ABPBI MW. The acid retention capability increased by 11% when the ABPBI MW reached 113 kDa. The fabricated ABPBI films exhibited good oxidative stability. A weight loss of only 9 wt% was observed for the high-MW ABPBI film compared to 19 wt% for the low-MW ABPBI film after 7 days in Fenton’s reagent at 65°C. The IEC increased with an order of magnitude when the ABPBI MW changed from 20 to 113 kDa. A maximum proton conductivity of 8.0 mS/cm was recorded for the high-MW film at 140°C, which was 45% higher than that for the low-MW ABPBI film. The proton conduction process followed the Grotthuss mechanism with a low activation energy (9.3 kJ mol) at the high-MW ABPBI film. These results indicated how important the ABPBI MW is in obtaining conductive films with remarkable properties for fuel cell (FC) applications. Prospectively, the findings of the current study can be implemented for other conductive polymers.

为了显示聚（2,5-苯并咪唑）（ABPBI）的分子量（MW）对其理化性质的影响，合成了一系列分子量从20到113 kDa的ABPBI聚合物，并将其制备成导电的电影。ABPBI薄膜的特征在于通过不同的光谱方法来测量酸负荷水平，酸保留能力，离子交换能力（IEC）和质子传导率。值得注意的是，磷酸（PA）的负载率随ABPBI MW的增加而增加。当ABPBI MW达到113 kDa时，酸保留能力提高了11％。所制备的ABPBI膜表现出良好的氧化稳定性。在65°C的Fenton试剂中放置7天后，高分子量ABPBI薄膜的重量损失仅为9重量％，而低分子量ABPBI薄膜的重量损失为19重量％。当ABPBI MW从20 kDa变为113 kDa时，IEC上升了一个数量级。在140°C时，高MW膜的最大质子传导率记录为8.0 mS / cm，比低MW ABPBI膜的质子传导率高45％。在高MW ABPBI膜上，质子传导过程遵循Grotthuss机理，具有低活化能（9.3 kJ mol）。这些结果表明，ABPBI MW对于获得具有卓越性能的燃料电池（FC）应用导电膜至关重要。潜在地，当前研究的结果可以用于其他导电聚合物。在高MW ABPBI膜上，质子传导过程遵循Grotthuss机理，具有低活化能（9.3 kJ mol）。这些结果表明，ABPBI MW对于获得具有卓越性能的燃料电池（FC）应用导电膜至关重要。潜在地，当前研究的结果可以用于其他导电聚合物。在高MW ABPBI膜上，质子传导过程遵循Grotthuss机理，具有低活化能（9.3 kJ mol）。这些结果表明，ABPBI MW对于获得具有卓越性能的燃料电池（FC）应用导电膜至关重要。潜在地，当前研究的结果可以用于其他导电聚合物。