Polybenzimidazolium hydroxides – Structure, stability and degradation

• Published in: Polymer degradation and stability Vol. 97; no. 3; pp. 264 - 272
• Main Authors: Henkensmeier, Dirk, Cho, Hyeong-Rae, Kim, Hyoung-Juhn, Nunes Kirchner, Carolina, Leppin, Janine, Dyck, Alexander, Jang, Jong Hyun, Cho, EunAe, Nam, Suk-Woo, Lim, Tae-Hoon
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.03.2012; Elsevier
• Subjects: 2-Phenyl-imidazolium hydroxide; anion exchange; Anion exchange membrane; Anion exchanging; Applied sciences; cations; chemical structure; Degradation; Ethers; Exact sciences and technology; fuel cells; Hydrolysis; Hydroxides; Iodides; NMR; nuclear magnetic resonance spectroscopy; Physicochemistry of polymers; Polybenzimidazole; Polymer electrolyte; Polymer industry, paints, wood; Stability; Technology of polymers; X-ray photoelectron spectroscopy; Hydrolysis; NMR; Polymer electrolyte; 2-Phenyl-imidazolium hydroxide; Polybenzimidazole; Anion exchange membrane; Molecular structure; Polymer solid electrolyte; Polymer; Fuel cell
• ISSN: 0141-3910
• DOI: 10.1016/j.polymdegradstab.2011.12.024

Polybenzimidazolium hydroxides are of potential interest for the use in alkaline anion exchange membrane fuel cells (AAEMFC). Introduction of an ether group in para-position of the 2-phenyl substituent improves the mesomeric stabilization of imidazolium cations, and O-PBI seems to be more stable than meta-PBI under alkaline conditions. NMR, IR and XPS analysis show a structural change when the iodide form is exchanged into the hydroxide form. Surprisingly, this structural change is subject to a pH sensitive equilibrium and the pure imidazolium form is retained immediately when the pH is lowered. The molecular structure at high pH is either the 2-carbinol or the amine–amide. Further hydrolysis necessitates excess hydroxide.