Cationic and anionic environments in mono-urethanesil hybrids doped with magnesium triflate

Journal article, 2004

Sol–gel derived poly(oxyethylene), POE/siloxane hybrids (mono-urethanesils) with a wide range of magnesium triflate (Mg(CF3SO3)2) concentrations were analyzed by infrared and Raman spectroscopies with the goal of examining the cation/polymer, cation/cross-link, hydrogen bonding and cation/anion interactions. In the host matrix of these xerogels short CH3-terminated POE segments are covalently bonded to the siliceous backbone through urethane linkages. Samples with ∞>n≥6 (where n is the molar ratio of (OCH2CH2) moieties per Mg2+ ion) were synthesized. The spectral data obtained provided conclusive evidence that the ether oxygen atoms of the polymer chains of the host structure complex the alkaline-earth ions in materials with n≤60. "Free" triflate ions and weakly coordinated anions were detected over the whole range of salt concentration examined. The coordinated triflate species are formed in two different bonding environments. Contact ion pairs appear in materials with n≤60. This work confirms previous studies that suggested that the nature of the cations added to the mono-urethanesil-type framework plays a key-role in the properties of these composites.