High Proton Conductivity in the Molecular Interlayerof a Polymer Nanosheet Multilayer Film.

High proton conductivitywas achieved in a polymer multilayer filmwith a well-defined two-dimensional lamella structure. The multilayerfilm was prepared by deposition of poly(N-dodecylacryamide-co-acrylic acid) (p(DDA/AA)) monolayers onto a solid substrateusing the Langmuir–Blodgett technique. Grazing-angle incidenceX-ray diffraction measurement of a 30-layer film of p(DDA/AA) showedstrong diffraction peaks in the out-of-plane direction at 2θ= 2.26° and 4.50°, revealing that the multilayer film hada highly uniform layered structure with a monolayer thickness of 2.0nm. The proton conductivity of the p(DDA/AA) multilayer film parallelto the layer plane direction was 0.051 S/cm at 60 °C and 98%relative humidity with a low activation energy of 0.35 eV, which iscomparable to perfluorosulfonic acid membranes. The high conductivityand low activation energy resulted from the formation of uniform two-dimensionalproton-conductive nanochannels in the hydrophilic regions of the multilayerfilm. The proton conductivity of the multilayer film perpendicularto the layer plane was determined to be 2.1 × 10–13S/cm. Therefore, the multilayer film showed large anisotropic conductivitywith an anisotropic ratio of 2.4 × 1011. [ABSTRACT FROM AUTHOR]