SMALL-ANGLE X-RAY-SCATTERING STUDY FOR STRUCTURAL-CHANGES OF THE ION CLUSTER IN A ZINC SALT OF AN ETHYLENE METHACRYLIC-ACID IONOMER ON WATER-ABSORPTION

The dimensional change of the ion cluster in a zinc salt of poly(ethylene-co-methacrylic acid) ionomer during moisture absorption was investigated by small-angle X-ray scattering (SAXS). Unlike the cases of previously investigated hygroscopic ionomers, the apparent peak position shifted toward the high-angle side with an increase in water content. The desmeared SAXS curves were analyzed in terms of the Percus-Yevick equation, and the structure parameters were derived by curve fitting. The observed change in SAXS with the absorbed water content was interpreted as follows. Although the intercluster distance increased a little with water content as expected, the interparticle interference and minor change in other structural parameters perturbed the scattering profile in an unexpected manner, since the scattering intensity was so weak. © 1990, American Chemical Society. All rights reserved.