Langmuir, Vol.31, No.18, 5174-5180, 2015
High Proton Conductivity in the Molecular Interlayer of a Polymer Nanosheet Multilayer Film
High proton conductivity Was achieved in a polymer multilayer film with a well-defined two dimensional lamella structure The multilayer film was prepared by deposition of poly(N-dodecylacryamide-co- acrylic acid) (p(DDA/AA)) monolayers onto a solid substrate using the Langmuir-Blodgett technique. Grazing-angle incidence X-ray diffraction measurement of a 30 layer film Of,p(DDA/AA) showed strong diffraction peaks in the-out-of-plane direction at 2 theta = 2.26 degrees and 4.50 degrees revealing that the multilayer film had a highly uniform layered structure with a monolayer thickness of 2.0 nm. Tho proton conductivity Of the p(DDA/AA) multilayer film. parallel to the layer plane direction was 0.051 S/cm at 60 degrees C and 98% relative-humidity with a low activation energy of 0.35 eV, which is comparable to perfluorosulfonic acid membranes. The high conductivity and low activation energy resulted from the formation of uniform two-dimensional proton-conductive nanochannels in:the hydrophilic regions of the multilayer film. The proton conductivity of the multilayer film perpendicular to the layer plane was determined to be 2.1 X 10(-13) S/cm. Therefore, the multilayer film showed large anisotropic conductivity with an anisotropic ratio of 2.4 x 10(11).