Characterization of Nafion as a Permselective Membrane by NMR
Abstract
NMR measurements were made on three classes of Nafion samples to characterize penetrant diffusion and morphology. Nafion-115 and 117 films in the acid form were swollen with dimethyl metbylphosphonate (DMMP). The translational motion of the DMMP was observed using pulse field gradient NMR and the domain size of the pendant group was measured using fluorine-19 spin diffusion under conditions of high speed magic angle spinning. Both the diffusion and the domain size measurements pointed to a change in the morphology as a function of DMMP concentration with the development of larger domains at high DMMP concentration. Similar measurements of Nafion swollen with water did not involve a change in morphology. Diffusion and morphological measurements were made on calcium neutralized N-115 swollen with DMMP. Large domains and rapid DMMP diffusion were observed. Lastly cast films of Nafion-112 were prepared with and without the addition of fumed silica nanoparticles. Diffusion of water, methanol and DMMP were measure in these cast films which appeared to have smaller domain sizes and increased selectivity for water over DMMP. Also the apparent diffusion constant of DMMP was a strong function of the time over which diffusion occurred indicating a domain structure obstructing translational motion.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 11, 2003
- Accession Number
- ADA423127
Entities
People
- Alan A. Jones
Organizations
- Clark University