Abstract
A new approach to get ordered and highly amine-functionalized organosilicas is described. The method consisted in using the reversible reaction between CO2 and amines giving rise to ammonium carbamate salts. Four amine containing precursors were selected for this study: 3-aminopropyltrimethoxysilane 1, 11-amino-undecyltrimethoxysilane 2, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane 3 and N-(6-aminohexyl)-3-aminopropyltrimethoxysilane 4. CO2 reacted with 1 and 2 giving rise to bis-silylated organosilica precursors containing ammonium carbamate salts in the core while reaction between CO2 and 3 or 4 led to a supramolecular network of silylated ammonium carbamate salts. The hydrolytic polycondensation of these carbamate derivatives by using the sol-gel process gave rise to hybrid materials with lamellar structure containing ammonium carbamate salts. Subsequent elimination of CO2 upon heating generated materials with free amino groups in which the long-range order was maintained. We showed that the structuration was promoted by van der Waals interactions between the long alkylene chains. Some complexation reactions and chemical transformations were achieved in order to investigate the accessibility of amino groups as well as the chelating capability of the materials