Studies on solution cast perfluorocarbonsulfonic acid ionomers

Tsatsas, Andreas T.; Risen, William M.

doi:10.1002/polb.1993.090310917

Cited by 14 publications

(5 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The changes at high activation temperatures are well correlated with the weight loss of samples, as seen in the TGA data for Nafion/H and Mo/Nafion-30 presented in Figure . The weight losses for Nafion/H at different temperatures are in line with data reported for Nafion/H films 1 X-band ESR spectra at 125 K of Mo/Nafion-2 for the indicated activation temperatures (1 h at each temperature).…”

Section: Resultssupporting

confidence: 86%

“…The weight losses for Nafion/H at different temperatures are in line with data reported for Nafion/H films. 31 The ESR signals from Mo 5+ measured in Mo/Nafion-10 and -30 were more intense but similar in shape to those measured for Mo/Nafion-2. In Figure 3 we present ESR spectra of Mo/ Nafion-30 at 125 K, including the vertical expansion (×30) of the signals in the high magnetic field range, together with simulated spectra calculated with Gaussian line shapes.…”

Section: Resultssupporting

confidence: 60%

See 1 more Smart Citation

Ligand Design by Ionomers. ESR of Mo^V in Perfluorinated Ionomer Supports

et al. 1996

View full text Add to dashboard Cite

Electron spin resonance (ESR) spectra of Mo 5+ in perfluorinated membranes (Nafion) neutralized by MoCl 5 suggest that the ionomer acts as an ion-selective medium and replaces the chlorine ligands of the molybdenum center by oxygen ligands from the sulfonic groups. This conclusion is based on an analysis of the ESR parameters that characterize the paramagnetic center and is supported by the detection of only one major paramagnetic molybdenum site, Mo(A) in the bulk ionomer, in the absence of solvents. Ligand design via the ionomer was thus achieved. We propose that the main molybdenum species is MoO(SO 3 -) 5 , where the unique oxygen ligand is from an sSdO group of the sulfonic moiety. Exposure of Mo/Nafion to water (up to 5 Torr) has no significant effect on the ESR parameters and on the intensity of the ESR signal. Exposure to 25 Torr of water leads to the reversible disappearance of the ESR signal. Brief exposure of Mo/Nafion to gaseous acetonitrile (as CD 3 CN) results in the appearance of two new Mo species, Mo(B) and Mo(C), which are thought to be formed via replacement of one equatorial or one axial sSdO ligand, respectively, based on an analysis of the effect on the corresponding g | values. Soaking of Mo/Nafion samples with acetonitrile results in the reversible disappearance of the ESR signals. All transformations of the ESR signals are explained by the replacement of one L-type ligand (donating two electrons), sSdO in the case of Nafion, by oxygen from water or by nitrogen from acetonitrile. The loss of the signal in the presence of adsorbates is explained by a replacement of one or more of the -S-O -ligands by ligands from the adsorbates. This process is a reversible reductive replacement of the ionic ligands and leads to the concomittant loss of the paramagnetism. The control of ligands around the paramagnetic center, the involvement of the molybdenum in redox processes, and the accessibility of the center to adsorbates are promising features for catalysis. Initial results for the oxidation of ethanol on Nafion and on Mo/Nafion supports are presented. Correlation plots (A | vs g | ) in paramagnetic molybdenum complexes, constructed from data in the literature and measured in this study, show trends that can be used for identification of the number and types of ligands in paramagnetic molybdenum centers.

show abstract

Section: Resultssupporting

confidence: 86%

Section: Resultssupporting

confidence: 60%

Ligand Design by Ionomers. ESR of Mo^V in Perfluorinated Ionomer Supports

et al. 1996

View full text Add to dashboard Cite

show abstract

“…The middle temperature endothermic enthalpy around 120-220 C can be attributed to the evaporation of water associated with sulfonic acid groups. The endothermic enthalpy around 200-260 C can be attributed to the dissociation of Nafion perfluorocarbon backbone aggregations [48][49][50]. However it is hard to separate three endothermic regions from DSC data, due to the overlap of these endothermic regions.…”

Section: Dsc Studymentioning

confidence: 96%

Morphology and properties of Nafion membranes prepared by solution casting

Hung

Lin

et al. 2009

Polymer

142

111

View full text Add to dashboard Cite

“…However, the morphology induced by phase separation is affected by various factors such as different states of hydration [23,24], specific intermolecular interactions [25], casting solvents [26], processing conditions of the membrane [27], hydrothermal history [23,28], etc. Most studies were focused on morphology investigation of hydrated Nafion film using small angle X-ray scattering (SAXS) and scanning probe microscopy (SPM) [29].…”

Section: Introductionmentioning

confidence: 99%