Chemical oxidation stability and anhydrous proton conductivity of polyimides/phosphoric acid/imidazole blends

Abstract Polyimides (PIs) based on 3,3′,4,4′‐tetracarboxylicdiphenyl ether dianhydride, 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride, 4,4′‐diaminodiphenylsulfone and 4,4′‐methylenedianiline were synthesized. They are easily dissolved in many strong and polar solvents like dimethylformamide, N , N ‐dimethylacetamide, 1‐methyl‐2‐pyrrolidinone, and dimethylsulfoxide. A new kind of anhydrous proton conducting system based on PI/H 3 PO 4 and PI/H 3 PO 4 /imidazole (Imi) blends was prepared. The chemical oxidation stability of the composite membranes was studied. The flexible PIs have better chemical oxidation stability. The addition of phosphoric acid can accelerate the degradation process of PIs, while the addition of Imi in PI/H 3 PO 4 blends can greatly improve their chemical oxidation stability, which becomes much better than that of pure PIs. The proton conductivity of PI/H 3 PO 4 blends is still lower compared with that of polybenzimidazole/H 3 PO 4 blends. After the addition of Imi, the anhydrous proton conductivity of PI/H 3 PO 4 blends increases significantly with increasing Imi content. Copyright © 2006 Society of Chemical Industry