Cation coordination in mono-urethanesil hybrids doped with sodium triflate

Infrared and Raman spectroscopies were used to elucidate the cation/polyether, cation/urethane, cation/anion and hydrogen bonding interactions occurring in poly(oxyethylene), POE/siloxane materials doped with sodium triflate (NaCF3SO3). The hybrid host matrix of these xerogels (mono-urethanesils) is composed of methyl terminated POE chains (with about 17 repeat units) grafted through urethane groups to the siliceous framework. Samples with n≥3 (where n is the molar ratio of oxyethylene moieties per Na+ ion) were examined. The results obtained demonstrate that the POE chains of the host framework participate actively in the complexation of the alkali ions in the mono-urethanesils with n≤10. In the more dilute compounds, while a few cations coordinate to the carbonyl oxygen atoms of the urethane linkages, the great majority will bond to the oxygen atoms of the triflate ions, producing ion contact pairs, negatively charged triplets and an ionic aggregate. In the xerogels with n=6 and 3, these ionic species coexist with positively charged triplets and another aggregate. The crystalline POE1.1NaCF3SO3 compound is formed in the latter materials. This study provides conclusive evidence that the nature of the cations incorporated in the mono-urethanesil-type structure plays a major role in the properties of these composites