Ionic Conduction in NanostructuredMembranes Basedon Polymerized Protic Ionic Liquids.

Polymerized ionic-liquids (PILs) are promising materialswhoseionic properties can be tuned based on their chemistry. By incorporatingPILs into block copolymer (BCP) structures, it is possible to providecomplementary functionality (i.e., structural stability) and transporttunability to ion-conducting materials. In this study, we describethe self-assembly and conductivity of novel poly(styrene-block-histamine methacrylamide) diblock copolymers (PS-b-PHMA) and the resulting PS-b-PIL derivatives obtainedafter treatment with trifluoroacetic acid (TFA). These materials self-assembleinto ordered BCP structures with tunable domain sizes as demonstratedby small-angle X-ray scattering (SAXS) and transmission electron microscopy(TEM). PS-b-PHMA membranes show conductivities upto 2 × 10–4S/cm at room temperature, whichincrease byan order of magnitude in the presence of acid. In addition, both PHMA-and PIL-based membranes exhibit lower water uptake (λ = 4–6and 8–10, respectively) in comparison with most proton conductingmembranes reported elsewhere. The low water content in these membranestranslates into a stronger effect of morphology on transport behavior,resulting in a measurable increase in ion conductivity as a functionof conducting channel size. [ABSTRACT FROM AUTHOR]