title: Vibrational spectroscopic study of pure and silica-doped sulfonated poly(ether ether ketone) membranes.
abstract: We report the vibrational properties of sulfonated poly(ether ether ketone) (SPEEK) membranes, used as electrolytes in proton exchange membrane (PEM) fuel cells, studied by Fourier transform infrared (FTIR) spectroscopy. We discuss the changes in the vibrational modes of the functional groups present in the polymer arising due to the sulfonation process and the subsequent incorporation of silica particles functionalized with sulfonic acid group. From the infrared spectra, we confirm the incorporation of sulfonic acid group in the polymer chain as well as in the functionalized silica particles. We have also measured the variations in the peak area ratio of the characteristic out-of-plane vibrations of the aromatic rings in the PEEK polymer at 1280cm(-1) with respect to a reference peak at 1305cm(-1). These values were correlated to the crystallinity (XC) values experimentally determined by DSC technique, providing a non-destructive means to calculate the crystallinity of polymer membranes. The calculated XC values were in good agreement with the experimental values. The crystallinity was observed to decrease with increasing degree of sulfonation (DS), indicating the crystalline-to-amorphous phase modification of the polymer by sulfonation, which along with the enhanced ion-exchange capacity and water uptake, is responsible for the improved ionic conductivity at higher DS values.
authors.affiliation: Department of Physics and Astronomy, KU Leuven, Bus 2414, Celestijnenlaan 200D, 3000 Leuven, Belgium. Electronic address: vijayshankar.rangasamy@fys.kuleuven.be.
authors.forename: Vijay Shankar
authors.initials: VS
authors.lastname: Rangasamy
authors.affiliation: Department of Physics and Astronomy, KU Leuven, Bus 2414, Celestijnenlaan 200D, 3000 Leuven, Belgium.
authors.forename: Savitha
authors.initials: S
authors.lastname: Thayumanasundaram
authors.affiliation: Department of Metallurgy and Materials Engineering, Kasteelpark Arenberg 44 - Bus 2450, B-3001 Leuven, Belgium.
authors.forename: Jin Won
authors.initials: JW
authors.lastname: Seo
authors.affiliation: Department of Physics and Astronomy, KU Leuven, Bus 2414, Celestijnenlaan 200D, 3000 Leuven, Belgium.
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Locquet
mesh_terms: D001577:Benzophenones; D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D007659:Ketones / Q000737:chemistry*; D008567:Membranes, Artificial; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers; D066244:Proton Magnetic Resonance Spectroscopy; D012822:Silicon Dioxide / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013451:Sulfonic Acids / Q000737:chemistry*; D013818:Thermogravimetry; D014732:Vibration
chemical_list: D001577:Benzophenones; D007659:Ketones; D008567:Membranes, Artificial; D011108:Polymers; D013451:Sulfonic Acids; C063834:polyetheretherketone; D011092:Polyethylene Glycols; D012822:Silicon Dioxide
keywords: Chalmers peak; Crystallinity; FTIR; SPEEK; Silica; Sulfonation