Ionic environment and hydrogen bonding in di-ureasil ormolytes doped with lithium triflate

Di-urea cross-linked sol-gel derived poly(oxyethylene) (POE)/siloxane hybrids (di-ureasils) doped with a wide concentration range of lithium triflate (LiCF₃SO₃) were studied by infrared and Raman spectroscopies with the primary objective of examining in detail the Li ⁺/cross-link and hydrogen bonding interactions. Another goal of this work was to find additional data that confirmed previous conclusions regarding the Li⁺/polymer and Li⁺/anion bonding. Xerogels with ∞>n≥1 (where n, called salt composition, is the molar ratio OCH ₂CH₂/Li⁺) were analyzed. The analysis of the 'amide I' and 'amide II' regions provided solid evidences that the Li ⁺ ions bond to the urea carbonyl oxygen atoms in the entire range of salt concentration studied. The changes detected in the CH₂ rocking region indicate that the alkali metal cations are also coordinated to the ether oxygen atoms of the POE chains at n≤20. Proofs of the formation of a POE/LiCF₃SO₃ crystalline compound at n≤10 were also found. The anionic configurations detected in the FT-IR SO₃ symmetric stretching region are in perfect agreement with those deduced from the FT-Raman spectra.