| Autor: |
Vezzù K; Section of Chemistry for Technology, Department of Industrial Engineering, University of Padova, in Department of Chemical Sciences , Via Marzolo 1, I-35131 Padova, Italy.; Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM) , Via Marzolo 9, I-35131 Padova, Italy., Maes AM; Department of Chemical and Biological Engineering, Colorado School of Mines , Golden, Colorado 80401-1887, United States., Bertasi F; Section of Chemistry for Technology, Department of Industrial Engineering, University of Padova, in Department of Chemical Sciences , Via Marzolo 1, I-35131 Padova, Italy.; Interdepartmental Centre Giorgio Levi Cases for Energy Economics and Technology , Via Marzolo 9, I-35131 Padova, Italy., Motz AR; Department of Chemical and Biological Engineering, Colorado School of Mines , Golden, Colorado 80401-1887, United States., Tsai TH; Department of Polymer Science and Engineering, University of Massachusetts Amherst , 120 Governors Drive, Amherst, Massachusetts 01003, United States., Coughlin EB; Department of Polymer Science and Engineering, University of Massachusetts Amherst , 120 Governors Drive, Amherst, Massachusetts 01003, United States., Herring AM; Department of Chemical and Biological Engineering, Colorado School of Mines , Golden, Colorado 80401-1887, United States., Di Noto V; Section of Chemistry for Technology, Department of Industrial Engineering, University of Padova, in Department of Chemical Sciences , Via Marzolo 1, I-35131 Padova, Italy.; Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM) , Via Marzolo 9, I-35131 Padova, Italy.; Interdepartmental Centre Giorgio Levi Cases for Energy Economics and Technology , Via Marzolo 9, I-35131 Padova, Italy.; Material Science and Engineering Department, University of Carlo III , Avenida De la Universidad, 30, 28911 Leganés, Madrid, Spain. |
| Abstrakt: |
Anion-exchange membranes (AEMs) consisting of poly(vinyl benzyl trimethylammonium)-b-poly(methylbutylene) of three different ion exchange capacities (IECs), 1.14, 1.64, and 2.03 mequiv g -1 , are studied by High-Resolution Thermogravimetry, Modulated Differential Scanning Calorimetry, Dynamic Mechanical Analysis, and Broadband Electrical Spectroscopy in their OH - form. The thermal stability and transitions are elucidated, showing a low temperature T g and a higher temperature transition assigned to a disorder-order transition, T δ , which depends on the IEC of the material. The electric response is analyzed in detail, allowing the identification of three polarizations (only two of which contribute significantly to the overall conductivity, σ EP and σ IP,1 ) and two dielectric relaxation events (β 1 and β 2 ), one associated with the tolyl side groups (β 1 ) and one with the cationic side chains (β 2 ). The obtained results are integrated in a coherent picture and a conductivity mechanism is proposed, involving two distinct conduction pathways, σ EP and σ IP,1 . Importantly, we observed a reordering of the ion pair dipoles which is responsible for the T δ at temperatures higher than 20 °C, which results in a dramatic decrease of the ionic conductivity. Clustering is highly implicated in the higher IEC membrane in the hydroxyl form, which reduces the efficiency of the anionic transport. |
