Nafion 1790, small angle

Gierke, T. D., Munn, G. E. and Wilson, F. C. 1981. The morphology in Nafion perfluorinated membrane products, as determined by wide-angle and small-angle x-ray studies. Journal of Polymer Science Polymer Physics 19 1687-1704. 

Unfortunately, the small-angle scattering techniques used in the investigations of Nafion morphology generally probe but a small region of reciprocal space and Fourier inversion methods of analyzing the... 

Roche and co-workers used SAXS and small-angle neutron scattering (SANS) to study the morphology of 1200 EW Nafion membranes in the acid and neutralized forms with a range of water contents. ... 

Figure 3.43. Structure of Nafion-115 at ambient humidity derived from small-angle X-ray spectroscopy. The lighter areas are cluster structures in the material. (Reprinted with permission from J. Elliott, S. Hanna, A. Elliott, G. Cooley (2000). Interpretation of the small-angle X-ray scattering from swollen and oriented perfluorinated ionomer membranes, Macromolecules 33, 4161-4171. Copyright American Chemical Society.)...

Figure 3. Small-angle x-ray scattering scans of hydrolyzed Nafion-Na with various equivalent weights. Samples are conditioned by boiling in 0.2Z NaOH for 1 h. Reproduced with permission from Ref. 25. Copyright 1981 John Wiley Sons, Inc.

Figure 6. Small-angle neutron scattering scans from Nafion acid with...

There is not much difference in T for the two doublets A and B, so ferric ion in both environments belongs to the same phase. Results on ferrous iron indicated that the ions are fully hydrated when the water content of the membrane exceeds 6 wt %, and partially hydrated at lower values. We conclude that the ions are entirely located in an aqueous phase in the Nafion membranes, and they are not directly incorporated in the crystalline or amorphous solid phases of the polymer. This is quite consistent with small angle scattering results (26). 

As in other ionomers, the ion exchange sites in "Nafion" membranes are observed to aggregate and form clusters. Ionic clustering in "Nafion" membranes has been indicated by a variety of physical studies including dielectric relaxation (1), small angle x-ray scattering (1-4), neutron scattering (4), electron micro-... 

A model of structure has been developped from electron microscopy and X-ray studies in Nafions (6). No basic difference exists between X-ray and neutron techniques. Nuclear interactions of neutrons with matter are characterized by the coherent scattering length and the corresponding values for H and D are very different Because of the different origins of the contrast, X-ray and neutron small angle scattering techniques are complementary. 

A more thorough investigation at intermediate humidity levels is needed. In addition, it is clear that a number of other studies including scattering at larger Q, quantitative investigations of intensities, and a comparison of small-angle neutron and x-ray results are needed to understand the complex structure present in hydrated Nafions. 

Figure 5. Small-angle neutron scattering (SANS) curves for an acid Nafion sample soaked in water with different HiO/DgO concentrations...

T.D. Gierke, G.E. Munn and EC. Wilson, Morphology of Nafion perfluorosulfonated membrane products, as determined by wide- and small-angle X-ray studies, J. Polym. Sci., Polym. Phys. Ed., 1981, 19, 1687-1704 W.Y. Hsu and T.D. Gierke, Elastic theory for ionic clustering in perfluorinated ionomers, Macromolecules, 1982, 15, 101-105. 

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