Vibrational Spectroscopic Monitoring of the Gelation Transition in Nafion Ionomer Dispersions
Year: 2020
Type: article
Abstract: Infrared and Raman spectroscopy techniques were applied to investigate the drying and aggregation behavior of Nafion ionomer particles dispersed in aqueous solution. Gravimetric measurements aided the identification of gel-phase development within a series of time-resolved spectra that tracked transformations of a dispersion sample during solvent evaporation. A spectral band characteristic of ionomer sidechain end group vibration provided a quantitative probe of the dispersion-to-gel change. For sets of attenuated total reflection Fourier transform infrared (ATR FT-IR) spectra, adherence to Beer's law was attributed to the relatively constant refractive index in the frequency region of hydrated –[Formula: see text] group vibrations as fluorocarbon-rich ionomer regions aggregate in forming the structural framework of membranes and thin films. Although vibrational bands associated with ionomer backbone CF 2 stretching vibrations were affected by distortion characteristic of wavelength-dependent refractive index change within a sample, the onset of band distortion signaled gel formation and coincided with ionomer mass % values just below the critical gelation point for Nafion aqueous dispersions. Similar temporal behavior was observed in confocal Raman microscopy experiments that monitored the formation of a thin ionomer film from an individual dispersion droplet. For the ATR FT-IR spectroscopy and confocal Raman microscopy techniques, intensity in the water H–O–H bending vibrational band dropped sharply at the ionomer critical gelation point and displayed a time dependence consistent with changes in water content derived from gravimetric measurements. The reported studies lay groundwork for examining the impact of dispersing solvents and above-ambient temperatures on fluorinated ionomer transformations that influence structural properties of dispersion-cast membranes and thin films.
Source: Applied Spectroscopy
Institutions: Texas Tech University, University of Utah
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,000
Awards: G4419393689, Collaborative Research:Advancing strategies for in-situ determination and spatial mapping of components within membrane systems for energy conversion, Collaborative Research:Advancing strategies for in-situ determination and spatial mapping of components within membrane systems for energy conversion, NEW GRANT - TIME RESOLVED ANALYTICAL METHODS FOR LIQUID/SOLID INTERFACES P.I. - JOEL M. HARRIS, G7424026288, G983000816
OpenAlex ID: W3044044951