Polybenzimidazoles pyridine-based

Xiao, L. et al.. Synthesis and characterization of pyridine-based polybenzimidazoles for high temperature polymer electrolyte membrane fuel cell applications. Fuel Cells, 5, 287, 2005. 

Lixiang, X. Zhang, H. Choe, E.-W. Scanlon, E. Ramanathan, L.S. Benicewicz, B.C. Synthesis and characterization of pyridine-based polybenzimidazoles as novel fuel cell membrane materials. Fuel Chem. Div. Prepr. 2003, 48, 447. 

In order to modify the state-of-the-art PBI stmcture and consequently its properties, significant effort has been focused on the synthesis of pyridine-based polybenzimidazoles. A systematic synthesis with different stractures was initiated to study the effect of the polymer molecular stmcture on the final film properties. The substitution of pyridine dicarboxylic acids (PDA) for the iso-/terephthalic acids is particularly interesting, because it increases the number of basic groups in the polymer backbones. The general stmcture of the series of pyridine-based polybenzimidazole (PPBI) homopolymers from 3,3 -4,4 -tetraaminobiphenyl (TAB) and 2,4-, 2,6-, 2,5- or 3,5-pyridine dicarboxylic acids using the PPA synthetic process is shown in Fig. 6. Monomer purity and accurate stoichiometry are cmcial to obtain high molecular weight polymers. 

A variety of high-temperature-resistant PBIs were synthesized and reported in the Uterature. The most widely used PBI is poly[2,2 -(l,3-phenylene)-5,5-benzimidazole] (known as m-PBI) [22]. The other variations are poly[2,2 -( 1,4- phenylene)-5,5 -benzimidazole] (known as p-PBI) [13], poly(4,4 -diphenylether-5,5 -bibenzimidazole) (OPBI) [23], poly(2,5-benzimidazole) (AB-PBI) [24], pyridine-based PBI [25], sulfonated PBI [26], hyperbranched polybenzimidazole (HPBI) [27], naphthalene-based PBI [28], fluorinated PBI [29], PBI block copolymer [30], sulfonated PBI copolymer with sulfone or sulfonic acid groups in the backbone [31,32], PBFnano-composite [33], cross-linked PBI [34], and many others. Different approaches have been taken by the researchers to modify the structure and properties of the fluorinated PBI. A detailed summary of these works is discussed below. 

Fig. 10.12 Chemical structure of repeat units for pyridine-based polybenzimidazoles...

Fig. 7.14 Temperature dependence of proton conductivity of a 2,5-PPBI membrane with 20.4 mol H3PO4 doping. Reprinted with permission from Ref. [54] L. Xiao, et al.. Synthesis and characterization of pyridine-based polybenzimidazole for high temperature polymer electrolyte membrane fuel cell application. Fuel Cell, 5, 287-295 (2005). Copyright Wiley-VCH...

Xiao, L., H. Zhang, T. Jana, E. Scanlon, R. Chen, E. W. Choe, L. S. Ramanathan, S. Yu, and B. C. Benicewicz, Synthesis and characterization of pyridine-based of polybenzimidazoles for high temperature polymer electrolyte membrane fuel cell applications . Fuel Cells 5(2) (2005) 287-295. 

The acid-base Nafion composite membranes include blends of Nafion with polypyrrole (PPy) [98-104], polybenzimidazole (PBI) [105-107], poly (propyleneoxide) (PPO) [108, 109], polyfurfuryl alcohol (PFA) [110], poly(vinyl alcohol) (PVA) [111-115], sulfonated phenol-formaldehyde (sPF) [116], polyvinylidene fluoride (PVdF) [117-122], poly(p-phenylene vinylene) (PPV) [123], poly(vinyl pyrrolidone) (PVP) [124] polyanifine (PANI) [125-128], polyethylene (PE) [129], poly(ethylene-terephtalate) [130], sulfated p-cyclodextrin (sCD) [131], sulfonated poly(ether ether ketone) (sPEEK) [132-135], sulfonated poly(aryl ether ketone) (sPAEK) [136], poly(arylene ether sulfone) (PAES) [137], poly(vinylimidazole) (PVl) [138], poly(vinyl pyridine) (PVPy) [139], poly (tetrafluoroethylene) (PTFE) [140-142], poly(fluorinated ethylene-propylene) [143], sulfonated polyhedral oligomeric silsesquioxane (sPOSS) [144], poly (3,4-ethylenedioxythiophene) (PEDT) [145, 146], polyrotaxanes (PR) [147], purple membrane [148], sulfonated polystyrene (PSSA) [149, 150], polystyrene-b-poly(ethylene-ran-butylene)-bpolystyrene (SEES) [151], poly(2-acrylamido-2-methyl-l-propanesulphonic acid-co-l,6-hexanediol propoxylate diacrylate-co-ethyl methacrylate) (AMPS) [152], and chitosan [31]. A binary PVA/chitosan [153] and a ternary Nafion composite with PVA, polyimide (PI) and 8-trimethoxy silylpropyl glycerin ether-1,3,6-pyrenetrisulfonic acid (TSPS) has also been reported [154]. 

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