Effects of temperature on aggregate local structure in a zinc-neutralized carboxylate ionomer

The aggregate structure of a zinc-neutralized ionomer made from an ethylene -methacrylic acid copolymer was studied as a function of temperature using extended X-ray absorption fine structure (EXAFS) spectroscopy. No gross cha nges in structure were found in the range 6-450 K, indicating that the aggr egate structure remains basically unperturbed over this temperature range u nder quiescent (no-stress) conditions. Changes in EXAFS spectra were assign ed to changes in mean-squared displacement with temperature as expected. At a temperature that corresponds roughly to the melting point of polyethylen e, an extremely slight change in EXAFS spectra occurred which might be evid ence of minor changes in average aggregate size. No evidence was found for any dramatic changes in structure such as an order-disorder transition or a cid salt formation.