Nafion in Dilute Solvent Systems: Dispersion or Solution?

Abstract

The morphology of Nafion (EW = 1000, Na⁺ form) in dilute solvents is investigated using small angle neutron scattering (SANS) and ¹⁹F NMR. SANS modeling indicates three types of particle morphology: (i) a well-defined cylindrical dispersion in glycerol and in ethylene glycol with different degrees of solvent penetration; (ii) a less-defined, highly solvated large particle (>200 nm) in water/isopropanol mixtures; and (iii) a random-coil conformation (true solution behavior) in <i>N</i>-methylpyrrolidone. These distinct morphological characteristics of Nafion are consistent with the main and side chain mobilities measured by ¹⁹F NMR.