| Abstract: | ![]()
Ionic aggregates in a series of Zn‐neutralized poly(styrene‐co‐styrene sulfonate) (SPS) random ionomers have been imaged using scanning transmission electron microscopy. The Zn‐rich aggregates were found to have two shapes: solid spheres (Type I) and shells or vesicles (Type II). Type I aggregates range in a maximum diameter from 4 to 10 nm, whereas Type II aggregates range in a maximum diameter from 9 to 55 nm with a vesicle wall thickness of ∼ 3 nm. Lightly neutralized ionomers exhibited only Type I aggregates, whereas higher neutralization levels exhibited both Type I and II aggregates. Lightly neutralized ionomers also showed evidence of macrophase separation at the micron size scale. These direct observations of ionic aggregates contradict previous interpretations of small‐angle X‐ray scattering data with respect to size, size dispersity, shape, and spatial distribution. In addition, the aggregates observed in SPS differ markedly from the nearly monodisperse ∼ 2‐nm spherical aggregates observed in Zn‐neutralized poly(ethylene‐co‐methacrylic acid). The presence of vesicular aggregates encourages a re‐examination of the morphologies and properties of styrenic ionomers. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 477–483, 2001 |
