Preparation Of Copolybenzimidazoles And Ionic Cross-linked Membranes Containing Phthalazinone Moieties

In this paper, several kinds of polybenzimidazole membranes containing the twist and noncoplanar phthalazinone moieties have been prepared based on the molecular design principle under the background of the application of phosphoric acid doped polybenzimidazole membranes in PEMFC. We studied the performance of membranes in order to find a novel membrane material with good properties in high temperature and low humidity in PEMFC application.1. A series of novel co-polybenzimidazoles containing the twist and noncoplanar phthalazinone moieties were synthesized by condensation of3.3’-diaminobenzidine (DAB) with4-(4-(4-(4-carboxyphenoxy)phenyl)-1-oxophthalazin-2(1H)-y1)benzoic acid (DHPZ-DA) and3,4-diaminobenzoic acid (DABA) in different ratio in polyphosphoric acid. The copolybenzimidazole membranes were prepared in NMP. These membranes were amorphous in nature and the temperatures for5%weight loss of the membranes was above524℃. When DHPZ-DA’s content is90%and the phosphoric acid doped level is10.5, its proton conductivity is13.6mS/cm at120℃and tensile strength is26.04MPa at room temperature. So it can be used in PEMFC in the future.2. The SPPESK containing the twist and noncoplanar phthalazinone moieties was synthesized. So we prepared different blend membranes which based on SPPESK and AB-PPBI-20in different ratio with NMP. They formed inter-and intra-molecular ionic interactions. These membranes were amorphous in nature and the temperatures for5%weight loss of the membranes was above420℃. When SPPESK’s content is15%and the phosphoric acid content is163.4%, its proton conductivity is16.1mS/cm at120℃and tensile strength is26.8MPa at room temperature. The ionic cross-linked membranes have higher tensile strength and proton conductivity compared with original copolymer membranes after tested.3. The SPPESKP containing the twist and noncoplanar phthalazinone moieties and phenyl-s-triazine was synthesized. So we prepared different blend membranes which based on SPPESKP and AB-PPBI-20in different ratio with NMP. They formed inter-and intra-molecular ionic interactions. These membranes were amorphous in nature and the temperatures for5%weight loss of the membranes was above430℃. When SPPESKP’s content is10%and the phosphoric acid content is166.6%. its proton conductivity is8.4mS/cm at160℃and tensile strength is25.2MPa at room temperature. The ionic cross-linked membranes have higher tensile strength and proton conductivity compared with original copolymer membranes after tested.