Investigation of new ion-conducting ORMOLYTES : structure and properties

Abstract

Two families of hybrid organic-inorganic composites exhibiting Li+ ionic conduction (ORMOLYTES) have been prepared by the sol-gel process. The first family, prepared from a mixture of 3-isocyanatopropyltriethoxysilane, O,O''Bis (2-aminopropyl)-polyethyleneglycol (or O,O'Bis (2-aminopropyl)-polypropyleneglycol) and lithium salt, presents chemical bonds between the organic and the inorganic phase and an ionic conductivity σ higher than 10-4 S m-1 at room temperature. Their properties have been related to their structure using liquid state NMR measurements of 7Li between -100°C and +100'°C and the DMTA technique. In the second family, prepared by ultrasonic method from a mixture of tetraethoxysilane (TEOS), polyethyleneglycol (PEG) and lithium salt, the organic and inorganic phases are not chemically bonded. Ionic conductivity σ has been studied as a function of the polymer chain length and concentration. Values of σ up to 10-2S m-1 at room temperature have been obtained (with a silica-PEG300 system, PEG/TEOS=40% in weight). Again, structure was investigated by liquid state 7Li NMR measurements.