AN INVESTIGATION OF THE HIGH-MOLECULAR-WEIGHT POLY(ETHYLENE OXIDE)-ZINC BROMIDE COMPLEXES

Structural characterization studies using Raman and i.r. spectroscopy and extended X-ray absorption fine structure (EXAFS) on the (PEO)(n)[( ZnBr2)(1-x)(LiBr)(x)] system (n = 20, 40; x = 0-0.8) are reported. Ram an spectroscopy reveals that the ionic species present in the complex depend on the Zn:Li ratio and the ether oxygen to metal ion ratio. Wit h increasing x values, the species vary from ZnBr2 to ZnBr3- to ZnBr42 -. EXAFS measurements confirm that the Zn-Br coordination number is hi gher for the (PEO)(n)[(ZnBr2)(1-x)(LiBr)(x)] system than the (PEO)(n)Z nBr2 system. In the (PEO)(20)[(ZnBr2)(0.2)(LiBr)(0.8)] composition, no oxygen neighbours of zinc are apparent while a significant Zn-O contr ibution is present in the (PEO)(40)[(ZnBr2)(0.6)(LiBr)(0.4)] and (PEO) (40)ZnBr2 complexes. Temperature dependent EXAFS measurements of (PEO) (20)[(ZnBr2)(0.2)(LiBr)(0.8)] show that ionic association is not alter ed with lowering of temperature. The effect of addition of tetraethyle ne glycol (TEG) and its dimethyl ether (TEGDME) to the complex is also reported. (C) 1997 Elsevier Science Ltd.