Intercalation and Grafting of n-Alkyl Phosphonates into Synthetic Hydrotalcites

The chloride ions of synthetic hydrotalcite [Zn(0.67)Al(0.33)(OH)(2)]Cl(0.33) 0.4H(2)O were fully exchanged with C(n)H(2n+1)PO(3)H(-) and C(n)H(2n+1)PO(3)(2-) anions (n=0, 1, 2, 3, 4) and the products obtained were characterised for their composition, X-ray diffraction powder patterns, FT-IR absorption spectra and thermal behaviour. n-Alkylphosphonate anions are accommodated in the interlayer region as a monomolecular film with the alkyl-chains almost perpendicular to the layer plane and an odd-even alternation of the interlayer distance, as a function of the number of carbon atoms in the alkyl-chain, is observed. As a consequence of a mild thermal treatment the hydrogenphosphonates react with the hydroxyls and attach themselves to the inorganic layer to produce novel Zn and Al hydroxy alkylphosphonates that are able to intercalate n-alkanols.