Cation coordination and hydrogen bonding in potassium and magnesium based-di-amidosil hybrids


Fourier transform mid-infrared and Raman spectroscopies were employed to elucidate the cation/alkylene chains, cation/cross-link, cation/anion interactions and hydrogen bonding occurring in amorphous di-amide cross-linked alkylene/siloxane hybrid materials (diamidosils) doped with potassium and magnesium triflates (KCF(3)SO(3) and Mg(CF(3)SO(3))(2), respectively). Materials with compositions infinity > n >= 5 (where it expresses the molar ratio of carbonyl oxygen atoms per guest cation) were investigated. The conformations (gauche) of the alkylene chains of the host di-amidosil matrix are not affected by the presence of the guest salt in both doped di-amidosil families. The K(+) and M(2+) ions coordinate to the carbonyl oxygen atoms of the amide cross-links within the whole range of salt concentration considered, leading to the saturation of the cross-linkages, to a redistribution of the amide-amide hydrogen-bonded aggregates of the host matrix and, in the case of the K(+)-doped sample with n = 10, to the formation of a new type of aggregate, stronger and more ordered than those detected at lower salt content. In both di-amidosil systems guest salt addition leads to the increase of ionic associated species and to a concomitant decrease of the concentration of "free" anions. (c) 2007 Elsevier B.V. All rights reserved.



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Nunes, SC; Bermudez, VD; Ostrovskii, D; Carlos, LD; Silva, MM; Smith, MJ

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