In this work, a multi-analytical approach involving nitrogen porosimetry, small angle
neutron and X-ray scattering, Fourier transform infrared (FTIR) and nuclear magnetic
resonance (NMR) spectroscopies, X-ray diffraction, thermal analysis and electron microscopy
was applied to organically modified silica-based xerogels obtained through the sol–gel
process. Starting from a tetraethoxysilane (TEOS) precursor, methyltriethoxysilane
(MTES) was added to the reaction mixture at two different pH values (2.0 and 4.5)
producing hybrid xerogels with different TEOS/MTES molar ratios. Significant differences
in the structure were revealed in terms of the chemical composition of the silica
network, hydrophilic/hydrophobic profile, particle dimension, pore shape/size and
surface characteristics. The combined use of structural characterization methods allowed
us to reveal a relation between the cavity dimensions, the synthesis pH value and
the grade of methyl substitution. The effect of the structural properties on the controlled
Captopril release efficiency has also been tested. This knowledge facilitates tailoring
the pore network for specific usage in biological/medical applications. Knowledge
on structural aspects, as reported in this work, represents a key starting point for
the production of high-performance silica-based hybrid materials showing enhanced
efficacy compared to bare silica prepared using only TEOS.
