Hexamethyl-p-terphenyl poly(benzimidazolium) (HMT-PMBI) is a hydroxide-resistant, high-performing anion-conducting polymer. Such materials are very interesting, as they may allow the use of hydrogen fuel cells without platinum-group catalysts [1]. We have investigated the structure of this material using small-angle x-ray scattering (SAXS,) small-angle neutron scattering (SANS,) and computational methods. Our SAXS results revealed three distinct length scales, which we assigned to ion-polymer, interchain, and monomer length scales. A molecular dynamics (MD) simulation reproduced these features of the scattering curve and corroborated our interpretations of them. No structure at larger length scales was observed; the lack of large watery regions, common in high-performance ion-exchange membranes, may contribute to the material’s remarkable mechanical stability.

[1] A.G. Wright and S. Holdcroft, ACS Macro Lett. 3, 444 (2014).