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Layered Ultrathin Proton Conductive Film Based on Polymer Nanosheet Assembly

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journal contribution
posted on 25.05.2011, 00:00 by Jun Matsui, Hiromu Miyata, Yu Hanaoka, Tokuji Miyashita
As described in this paper, a layered ultrathin proton conductive film was prepared using a poly(N-dodecylacrylamide-co-2-acrylamido-2-methylpropanesulfonic acid) (p(DDA/AMPS)) polymer nanosheet. The surface pressure–area isotherm revealed that p(DDA/AMPS) formed a stable monolayer at the air–water interface. The polymer monolayer was transferred onto a solid substrate using the Langmuir–Blodgett technique. X-ray diffraction measurements of a 30-layer film of p(DDA/AMPS) showed clear Kiessig fringes and one Bragg peak, which indicate that the multilayer film took a uniform layered structure. The monolayer thickness was determined as 1.85 nm from the Bragg peak. The proton conductivity of p(DDA/AMPS) polymer nanosheet through the layer plane direction was studied with changing temperature and relative humidity. The proton conductivity of the multilayer film was on the order of 1 × 10–5 S/cm at 100% RH with 20 °C and increased to 1 × 10–2 S/cm at 70 °C. The proton conductivity of the multilayer film showed a more than 10 times higher value than that of the spin-coated film because of the formation of a uniform and consecutive hydrophilic nanochannel through the hydrophilic region in the multilayer film.