Proton‐conducting polymers based on benzimidazoles and sulfonated benzimidazoles

Abstract

A sulfonated derivative of polybenzimidazole is reported, and its properties are analyzed in comparison with related polybenzimidazole proton‐conducting materials. Poly(2,5‐benzimidazole), poly(m‐phenylenebenzobisimidazole), and poly[m‐(5‐sulfo)‐phenylenebenzobisimidazole] were prepared by condensation of the corresponding monomers in polyphosphoric acid. Several adducts of these polymers with phosphoric acid were prepared. The resulting materials were characterized by chemical analysis, Fourier transform infrared spectroscopy, and thermogravimetric analysis; also, the dc conductivity of doped and undoped derivatives was measured. Similar to what has been observed for the commercial polybenzimidazole polymer (also examined here for comparison), the title polymers exhibit high thermal stability. Furthermore, their doping with phosphoric acid leads to a significant increase in conductivity from less than 10−11 Scm−1 for the undoped polymers to 10−4 Scm−1 (both at room temperature) for their acid‐loaded derivatives. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3703–3710, 2002

Sulfonated Polybenzimidazoles for High Temperature PEM Fuel Cells

“…These values are significantly higher than those reported in the literature to date for conventionally prepared PBI membranes. Sulfonated PBIs that have been previously produced and doped with phosphoric acid typically contain 2-8 mol PA/PBI 30,33,35,38,41,46,47 which is considerably lower than the membranes produced via the PPA Process. The s-PBI membranes retain excellent mechanical properties, even at high doping levels.…”

“…The sulfonated PBIs (s-PBIs) have typically been proposed as Nafion alternatives and most characterization has been done with water as an electrolyte, [29][30][31]34,39,40,[43][44][45][46][47][48] but a small amount of investigation into PA-doped s-PBIs has been performed. 30,33,38,41,44,46,47 Structures that have been studied include grafting of aryl-or alkyl-sulfonates to the imidazole moiety, postsulfonation onto the biphenyl or diacid phenyl ring, copolymers of sulfonated PBI-type polymers with other sulfonated polymers, postsulfonation of PBI-type polymers with ether linkages incorporated into the backbone, and PBIs made with a sulfonated tetraamine.…”

“…30,33,38,41,44,46,47 Structures that have been studied include grafting of aryl-or alkyl-sulfonates to the imidazole moiety, postsulfonation onto the biphenyl or diacid phenyl ring, copolymers of sulfonated PBI-type polymers with other sulfonated polymers, postsulfonation of PBI-type polymers with ether linkages incorporated into the backbone, and PBIs made with a sulfonated tetraamine. Initial results show these polymers to be promising low or high temperature membranes, depending on the dopant.…”

“…13,[29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] Three common approaches are typically employed for functionalizing PBI: (1) direct sulfonation of the backbone, 29,47,49 (2)chemical grafting of functionalized monomers, 31,35 or (3) polycondensation of a sulfonated aromatic diacid with an aromatic tetraamine. 30,50 The last method provides advantages over the first two, such as limitation of side reactions and control over the degree of sulfonation. Previously published work has focused on modification of the m-PBI backbone structure.…”

Nanostructure, Morphology, and Properties of Fluorous Copolymers Bearing Ionic Grafts

“…Over the past decade, significant research effort has been devoted to the design of alternate membrane materials with the intention of improving properties and lowering cost. [2][3][4][5][6][7] A wide variety of different polymer systems have been examined including perfluorinated ionomers, 5,8 partially fluorinated ionomers, [9][10][11][12][13][14] polystyrene-based systems, [15][16][17][18][19][20][21][22] poly(arylene ether)s, [23][24][25][26][27][28] polyimides, [29][30][31][32][33] polybenzimidazoles, [34][35][36][37] and polyphosphazenes. [38][39][40][41] Despite this growing body of research, there exists a void in our understanding of fundamental structure-property relationships of PEMs in terms of the role of microstructure on morphology and the role of morphology on a membrane's property.…”