Various nanostructured amorphous silicas [fumed silicas such as crude (A-300), hydro-compacted (cA-300, TS 100), and precipitated silica Syloid 244] were modified by different polydimethylsiloxanes such as PDMS5, PDMS100, PDMS200, PDMS1000, and PDMS12500 (the label numbers show the viscosity (η) values) using dimethyl carbonate (DMC) as a siloxane-bond-breaking reagent. In addition, hexamethyldisilazane was used to modify fumed silica cA-300. The nanocomposites were characterized using microscopy, infrared spectroscopy, thermodesorption, nitrogen adsorption–desorption, solid-state NMR spectroscopy, small-angle X-ray scattering, and zeta-potential methods. It was found that the morphological, textural, and structural characteristics of silicas grafted with PDMS depend strongly not only on the type and content of the polymers used but also on the organization of nonporous nanoparticles (NPNP) in secondary structures (aggregates of NPNP and agglomerated aggregates, ANPNP), as well on the reaction temperature (Tr). Specifically, we determined that ANPNP with a macro/mesoporous character are favorable for the effective modification of the silicasstudied with short polymers and no DMC addition but at higher temperaturesor for a longer silicone polymer with the presence of DMC and at lowertemperatures. In particular, the PDMS/DMC-modified silicas are ofgreat interest from a practical point of view because they remainin a dispersed state with no strong compaction of the secondary structuresafter modification, and this corresponds to a better distributionof the modified nanoparticles in polymeric or other matrices.
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