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Polybenzimidazoles/Phosphoric Acid Solid Polymer Electrolytes: Mechanical and Electrical Properties

Published online by Cambridge University Press:  10 February 2011

M. Litt ,
R. Ameri ,
Y. Wang ,
R. Savinell  and
J. Wainwright
M. Litt
Affiliation:
Macromolecular Science Dept. and Chemical Engineering Dept., Case Western Reserve University, Cleveland, OH 44106-7202, mhl2@po.cwru.edu
R. Ameri
Affiliation:
Macromolecular Science Dept. and Chemical Engineering Dept., Case Western Reserve University, Cleveland, OH 44106-7202
Y. Wang
Affiliation:
Macromolecular Science Dept. and Chemical Engineering Dept., Case Western Reserve University, Cleveland, OH 44106-7202
R. Savinell
Affiliation:
Chemical Engineering Dept., Case Western Reserve University, Cleveland, OH 44106-7202
J. Wainwright
Affiliation:
Chemical Engineering Dept., Case Western Reserve University, Cleveland, OH 44106-7202
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Abstract

Poly (2,2'-(m-phenylene) 5,5'-bibenzimidazole), PBI and poly (2,5-benzimidazole), ABPBI, were cast into films and doped with phosphoric acid. Their mechanical properties were studied as a function of inherent viscosity and phosphoric acid content. The commercial PBI with an I. V. of 0.8 to 0.9 had relatively low elongation at break. It was fractionated; the higher the inherent viscosity the higher the modulus and elongation. At low phosphoric acid doping the modulus rose because a crystalline phase developed, and then dropped as more phosphoric acid was added. A second doping method produced films with high crystallinity and higher conductivity (0.02-.03 vs. 0.06-.08 S/cm) but poorer elongation than those made by doping a cast film in phosphoric acid. In order to get higher molecular weight films that could have better mechanical properties, we decided to polymerize 3,4-diaminobenzoic acid to ABPBI, an AB polymer for which I. V.'s of∼16 have been reported. After learning how to purify and polymerize the monomer, I. V.'s of 6–8 were easily obtained. Conductivities of the doped ABPBI films were as high as those of the best PBI films. With their high viscosities, the ABPBI films were much tougher and had better elongation than the doped PBI films.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 548: Symposia EE – Solid State Ionics V , 1998 , 313
Copyright
Copyright © Materials Research Society 1999

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References

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