DIFFERENTIAL ANOMALOUS X-RAY-SCATTERING FROM AN AMORPHOUS POLYMER ELECTROLYTE - [PPO]XZNBR2

Differential anomalous X-ray scattering (DAS) and extended X-ray absor ption fine structure (EXAFS) were used to determine the local structur e surrounding the ions in amorphous polymer electrolyte complexes of p oly(propylene oxide) and ZnBr2: [PPO]6ZnBr2 and [PPO]16ZnBr2. On the b asis of our results, we propose that ZnBr2 dissociates to form mainly ZnBr42- and Zn(O)(4)(2)+, where (O) is an ether oxygen on a PPO chain. This observation is contrasted with aqueous ZnBr2, where ZnBr2, ZnBr3 -, and ZnBr42- are all observed in the estimated proportions of 2:4:3, respectively. This paper describes the DAS method and its application to structure determination in a multicomponent, amorphous system. In systems with n components, where one or more of the species is a heavy atom, DAS reduces the scattering intensity from a weighted sum of n(n + 1)/2 partial structure factors to a sum of partial structure factor s which only include the heavy atom of interest.