Structure of ionic aggregates of ionomers. 1. Variation in the structure of ionic aggregates with different acid content and degree of neutralizationof ethylene and styrene ionomers

Small-angle X-ray scattering profiles of the ethylene and styrene ionomers were Studied to clarify the structure of ionic aggregates as a functions of the nature of cations, acid content, and degree of neutralization. The ion ic cluster peak was observed for the ionomers with a certain degree of neut ralization. The scattering profile of the ionic cluster peak was analyzed b y the modified hard-sphere model proposed by Yarusso and Cooper, and the si ze of ionic aggregates, closest approach distance between the aggregates, a nd average system volume per ionic aggregate were obtained. The size and di stance of the ionic aggregates in the ionomers with monovalent cation, sodi um and potassium cations, increased with the ion content (acid content x de gree of neutralization), while those with divalent one, zinc and copper cat ions, and trivalent one, ferric cation, changed only slightly. The number o f cations in an ionic aggregate was evaluated in an approximate manner by u sing the average system volume per ionic aggregate and the density of ionom er or the size of the ionic aggregate and the density of the ionic aggregat e estimated by a simple additivity rule for each phase.