Effect of silica and water content on the glass transition of poly(ethylene glycol) monomethylether-silica gel-lithium perchlorate ormolytes

The effect of silica and water content on the glass transition temperature, Tg, of MPEG2000-silica-LiClO4 ormolytes was assessed by differential scanning calorimetry (DSC). The sol-gel synthesized ormolytes consisted of various amounts of poly(ethylene glycol) monomethylether (M.W. = 2000 g/mol; i.e., MPEG2000) tethered to silica gel through the hydroxyl terminus via a urethane linkage. DSC features corresponding to physisorbed and hydrogen-bonded water, as well as the glass transition of the polyether, were identified. Both silica and LiClO4 raise the Tg and suppress crystallization of the polyether component. Water plasticizes the polyether and stoichiometrically solvates and sequesters Li+, thereby, lowering Tg.