Self-assembly of layered organosilicas based on weak intermolecular interactions

Abstract

New layered hybrid organic–inorganic materials were obtained directly by hydrolysis and polycondensation of monosilylated precursors of type (EtO)₃Si(CH₂)₃NH(CO)NHC_nH_2n+1 (n = 3, 8, 12 and 16). These precursors were easily prepared by reaction between commercially available triethoxysilylpropylisocyanate and primary aminoalkanes. The obtained materials were characterized by combining elemental analysis, X-ray powder diffraction, ¹³C, ²⁹Si NMR and FT-IR spectroscopies. They were found to be well condensed, and stable in water. We showed that their formation results from a cooperative effect between hydrogen bonding interactions originating from ureido groups and hydrophobic interactions between the long alkyl chains. There is no formation of material when n = 2, or from (EtO)₃SiC_nH_2n+1 when n = 18, thus proving that both types of weak intermolecular interactions are required. The chelating property of these materials towards europium(III) ions was tested.