Silica-PEG hybrid ormolytes: structure and properties

The effect of lithium salt doping on the structure and ionic conduction pro perties of silica-polyethyleneglycol composites is reported. These material s, so called ormolytes (organically modified electrolytes), were obtained b y the sol-gel process. They have chemical stability due to the covalent bon ds between the inorganic (silica) and organic (polymer) phase. The structur e of these hybrid materials was investigated by small-angle X-ray scatterin g (SAXS) as a function of lithium concentration [O]/[Li] (O being the oxyge ns of the ether type). The spectra have a well-defined peak attributed to t he existence of a liquid-like spatial correlation of silica clusters. The i onic conductivity was studied by AC impedance spectroscopy and is maximum f or [O]/[Li] = 15. This result is consistent with SAXS and thermo-mechanical analysis measurements and is due to the formation of cross-linking between the polymer chains for the larger lithium concentrations. These materials are solid, transparent, flexible and have an ionic conductivity up to 10(-4 ) S/cm. (C) 1999 Elsevier Science B.V. All rights reserved.