Di-ureasil hybrids doped with LiBF4 : spectroscopic study of the ionic interact...

• Author(s): Fernandes, Mariana ; Barbosa, P. C. ; Silva, Maria Manuela ; Smith, Michael John ; Zea Bermudez, V. de
• Date: 2011
• Persistent ID: http://hdl.handle.net/1822/15077
• Origin: RepositóriUM - Universidade do Minho
• Subject(s): Di-ureasils; Lithium tetrafluoroborate; FTIR; FT-Raman
• Document Type: Article
• Language: English

Description

In the present work Fourier Transform infrared and Raman spectroscopy were used to characterize the cation/polymer, cation/cross-link, cation/anion and hydrogen bonding interactions in hybrid electrolytes composed of lithium tetrafluoroborate (LiBF4) and di-urea cross-linked poly(oxyethylene) (POE)/siloxane hybrid networks (di-ureasils) designated as d-(2000) and d-U(600) and incorporating polyether chains with ca. 40.5 and 8.5 oxyethylene repeat units, respectively. Samples with ∞ > n ≥ 2.5 (where n, composition, is the molar ratio of CH2CH2O units per Li+ ion) were analyzed. In both di-ureasil systems over the whole range of salt content examined the Li+ ions bond to the ether oxygen atoms of amorphous POE chains and to BF4- ions forming ion contact pairs. Spectroscopic evidences and SEM images confirm the presence of a crystalline POE/LiBF4 complex of unknown stoichiometry at n < 20 and 25, respectively. Ionic association is particularly important in the case of the d-U(600)-based materials, as a result of the presence of strong hydrogen-bonded aggregates that prevent the establishment of Li+/urea carbonyl oxygen atom interactions.