Abstract
The reactivity of residual acetoxy and trimethylsilyloxy groups is studied in order to introduce new moieties into the surface of silicophosphates.
Highlights
Chemical modification of the surfaces of inorganic supports is a common method for the fabrication of a broad spectrum of surface-engineered materials, such as chemical and biological sensors, modified electrodes, separation membranes, selective adsorbents, sorbents for HPLC, heterogeneous metal-complex catalysts, biocompatible materials, and anti-adherent or anticorrosion coatings.1 The most widely used materials are based on silica, which can be chemically modified with organosilicon compounds
In the first part we focus on the detailed description of reaction pathways between residual organic groups on the surface of silicophosphate xerogels and various modifiers (H2O, hexamethyldisiloxane, POCl3, SiCl4, AlMe3, Al(NMe2)3 and AlCl3)
One is formed by coordination of phosphoryl oxygens (À213 ppm) and the other by carboxylic oxygen of acetate (À194 ppm).18,19. It is clear from the comparison of IR spectra before and after hydrolysis that acetoxy groups are depleted (eqn (7)) in the course of the reaction as indicated by the diminished intensity of the to OQP(OH)2(OSi) moieties.26,27. Based on these NMR data we conclude that hydrolysis of the skeletal RSi–O–PR bonds takes place (eqn (10)) to a large extent and the structure of silicophosphate xerogels collapses
Summary
Chemical modification of the surfaces of inorganic supports is a common method for the fabrication of a broad spectrum of surface-engineered materials, such as chemical and biological sensors, modified electrodes, separation membranes, selective adsorbents, sorbents for HPLC, heterogeneous metal-complex catalysts, biocompatible materials, and anti-adherent or anticorrosion coatings.1 The most widely used materials are based on silica, which can be chemically modified with organosilicon compounds. One is formed by coordination of phosphoryl oxygens (À213 ppm) and the other by carboxylic oxygen of acetate (À194 ppm).18,19 It is clear from the comparison of IR spectra before and after hydrolysis that acetoxy groups are depleted (eqn (7)) in the course of the reaction as indicated by the diminished intensity of the to OQP(OH)2(OSi) moieties.26,27 Based on these NMR data we conclude that hydrolysis of the skeletal RSi–O–PR bonds takes place (eqn (10)) to a large extent and the structure of silicophosphate xerogels collapses.
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