Structural and Free Volume Characterization of Sol–gel Organic–inorganic Hybrids, Obtained by Co‐condensation of Two Ureasilicate Stoichiometric Precursors

In this study two hybrid organic-inorganic ureasilicate monomers with different length of polymer segments were chosen for preparation of sol-gel material that includes two moieties blended on the molecular scale. The first monomer was obtained by crosslinking a double terminated polyoxyalkyleneamine with an isocyanate modified silicone ethoxide and the second one - by crosslinking between the isocyanate modified silicone ethoxide with an amino modified silicone ethoxide. Sol-gel route was applied for transformation of the liquid monomer blends in transparent materials with varying degree of rigidity. The prepared samples were characterized by small-angle X-ray scattering, Fourier-transform infrared spectroscopy, positron annihilation lifetime spectroscopy, and swelling experiments. The results demonstrate that the structure of the obtained materials could be tuned by a simple variation of molar fraction ratio between these two monomers. This makes it possible to obtain nanostructured materials with predictable properties.