SAXS study on ionic aggregates of styrene-isoprene-sulfonated isoprene terpolymer ionomer

The small-angle X-ray scattering profile of styrene-isoprene-sulfonated iso prene terpolymer ionomers was studied to clarify the structure of ionic agg regates at ambient temperature as a function of the degree of neutralizatio n of Na or Mg cations. An ionic cluster peak was observed for ionomers with a degree of neutralization greater than 25%. The ionic cluster peak was an alyzed by the modified hard sphere model proposed by Yarusso and Cooper [Ma cromolecules, 1983, 16, 1871], and the size of the ion cluster, the closest approach distance between the clusters, and the average system volume per ion cluster were evaluated by a curve-fitting method. The size of the ion c lusters of the ionomer with monovalent Na cation increased with the degree of neutralization, but for divalent Mg cation slightly changed. The number of ion clusters of the styrene-isoprene-sulfonated isoprene ionomer with Na and Mg cations characteristically increased with the neutralization. (C) 2 000 John Wiley & Sons, Inc.