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Characterisation of ion transport in sulfonate based ionomer systems containing lithium and quaternary ammonium cations
journal contributionposted on 2015-01-01, 00:00 authored by Yogita Vijaykumar Oza, D R MacFarlane, Maria ForsythMaria Forsyth, Luke O'DellLuke O'Dell
Two sulfonated ionomers based on poly(triethylmethyl ammonium 2-acrylamido-2-methyl-1-propane sulfonic acid) (PAMPS) and containing mixtures of Li+ and quaternary ammonium cations are characterised. The first system contains Li+ and the methyltriethyl ammonium cation (N1222) in a 1:9 molar ratio, and the 7Li NMR line widths showed that the Li+ ions are mobile in this system below the glass transition temperature (105°C) and are therefore decoupled from the polymer segmental motion. The conductivity in this system was measured as 10-5 Scm-1 at 130°C. A second PAMPS system containing Li+ and the dimethylbutylmethoxyethyl ammonium cation (N114(2O1)) in a 2:8 molar ratio showed much lower conductivities despite a significantly lower Tg (60°C), possibly due to associations between the Li+ and the ether group on the ammonium cation, or between the latter cations and the sulfonate groups.