Solid-state NMR was used to establish the specific intermolecular interactions responsible for the miscibility of blends of nylon 6 (PA6) and the zinc salt of lightly sulfonated polystyrene (Zn-SPS) and to characterize the scale of molecular mixing. 13C CP/MAS spectroscopy identified the interpolymer interaction as a complex between the Zn2+ cation of the ionomer and the amide nitrogen. Measurements of the spin-lattice relaxation times, TiH and 7\,H, indicated that mixing of the two polymers in the amorphous phase occurred at least down to a size scale of 2 nm. Ti"H measurements also revealed a microphase of >2.5-3.5 nm in the neat ionomer, which is consistent with the size of ionic domains inferred from previous small-angle X-ray (SAXS) measurements. Adding PA6 to Zn-SPS reduced the microheterogeneity in the ionomer as measured by Tlp.

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