The propylethylenediamine moiety was anchored on silica in acid medium by using sol-gel methodology. A sequence of reactions was carried out with glutaraldehyde followed by ethylenediamine in order to increase the organic chain pendant groups covalently bonded to the inorganic support. All synthesized silicas were characterized by carbon and nitrogen elemental analyses, thermogravimetry, differential scanning calorimetry, solid state C-13 and Si-29 NMR, and calorimetry. These analyses and techniques quantitatively confirmed all reaction steps. The results found strongly indicated that some silanol groups are converted to siloxane, which presented a great stability toward ring opening in aqueous medium.