Topic
Nafion
About: Nafion is a research topic. Over the lifetime, 9110 publications have been published within this topic receiving 320865 citations.
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TL;DR: In this paper, a composite membrane consisting of polyvinylidene fluoride (PVdF) and Nafion has been prepared by impregnating various amounts of Nafions into the pores of electrospun PVdF and characterized by scanning electron microscopy, differential scanning calorimetry, X-ray diffraction and proton conductivity measurements.
111 citations
TL;DR: NMR and ATR-FTIR spectroscopy, together with determination of ion exchange capacity, water uptake, proton conductivity, and fluoride ion release, strongly indicate that attack by H(•) occurs at the tertiary carbon C-F bond on both the main and side chain; whereas attack by HO( •) occurs solely on the side chain.
Abstract: Selective formation and reactivity of hydrogen (H(•)) and hydroxyl (HO(•)) radicals with perfluorinated sulfonated ionomer membrane, Nafion 211, is described. Selective formation of radicals was achieved by electron beam irradiation of aqueous solutions of H2O2 or H2SO4 to form HO(•) and H(•), respectively, and confirmed by ESR spectroscopy using a spin trap. The structure of Nafion 211 after reaction with H(•) or HO(•) was determined using calibrated (19)F magic angle spinning NMR spectroscopy. Soluble residues of degradation were analyzed by liquid and solid-state NMR. NMR and ATR-FTIR spectroscopy, together with determination of ion exchange capacity, water uptake, proton conductivity, and fluoride ion release, strongly indicate that attack by H(•) occurs at the tertiary carbon C-F bond on both the main and side chain; whereas attack by HO(•) occurs solely on the side chain, specifically, the α-O-C bond.
111 citations
TL;DR: In this article, the influence of membrane thickness on gas permeability and incorporation of cations on water content and ac specific resistance of Flemion® and Nafion®117 were estimated.
111 citations
TL;DR: In this paper, the nature of water in acid-form Nafion 117 was quantified at several hydration levels by dielectric relaxation spectroscopy, and the fastest process observed was identified as the cooperative picosecond relaxation of free (isotropic, bulklike) water, whereas the slowest process corresponded to water molecules strongly bound to the charged sulfonic groups.
Abstract: The nature of water in acid-form Nafion 117 was quantified at several hydration levels by dielectric relaxation spectroscopy. Two independent experimental setups were used to collect complex dielectric permittivity spectra at low frequencies (0.01 Hz to 1 MHz at -80 to 25°C) and in the microwave region (0.40-26 GHz at 25-45°C). We directly observed the states of water, manifested through three population averages with distinctly resolved dynamical behaviors, and their changes with temperature and hydration level. The fastest process observed was identified as the cooperative picosecond relaxation of free (isotropic, bulklike) water, whereas the slowest process (microsecond relaxation times) corresponded to water molecules strongly bound to the charged sulfonic groups. A third type of water was also observed, also characterized by picosecond relaxation times, close to and about three times slower than those of bulk water, which was attributed to loosely bound water and may contain substantial dynamical heterogeneities.
110 citations
TL;DR: In this article, the initial slope of the stress-strain curves decreases with increasing water contents in the Nafion membrane and also with the addition of methanol, ethanol and ethanol/water (50/50, v/v) mixture.
Abstract: Nafion membranes have been studied using dynamic mechanical analysis in the controlled force mode and clamp of tension film measurements for as received commercial Nafion membranes with different solvent contents and with different cations (Li+, Na+, K+, Rb+ and Cs+). In comparison with as-received Nafion membranes, the initial slope of the stress-strain curves decreases with increasing water contents in the Nafion membrane and also with the addition of methanol, ethanol and ethanol/water (50/50%, v/v) mixture. The initial slope decreases also with increasing temperatures. On the other hand, the initial slope increases when the cation is replaced, in the following order: Li+, Na+, K+, Cs+ and Rb+. Nafion in salt form normally shows an increase in the initial slope from room temperature up to approximately 90oC, after which the slope decreases with increasing temperatures.
110 citations