SMALL-ANGLE X-RAY-SCATTERING STUDIES OF NAFION(R) [SILICON OXIDE] ANDNAFION(R)/ORMOSLL NANOCOMPOSITES/

The small angle X-ray scattering technique was used to probe structura l heterogeneity on the scale of nanometers within Nafion(R)/[silicon o xide], Nafion(R)/[ORMOSIL], and Nafion(R)/[dimethylsiloxane] hybrid me mbranes. The results of this study reinforced the working hypothesis o f morphological template action for the tn situ growth of silicon oxid e, or organically modified silicon oxide phases in perfluorosulfonate ionomers via sol-gel reactions for silicon alkoxide or/and silicon alk ylalkoxide precursors. Nanophase separation persists when incorporated silicon oxide particles are postreacted with ethoxytrimethylsilane bu t postreaction with diethoxydimethylsilane generates co-continuous pha ses that do not generate ionomer SAXS peaks, presumably due to a more homogeneous Si atom distribution within the ionomer. These hybrids are true nanocomposites, as structural heterogeneity exists on the scale of similar to 5 nm. The variation of the small angle upturn for these hybrids is explained in terms of long-range inhomogeneities in ionomer s. (C) 1996 John Wiley & Sons, Inc.