Morphology, glass transition and molecular dynamics of polydimethylsiloxane (PDMS) adsorbed onto three types of silica nanoparticles, namely Stober, fumed-pyrogenic, and silica gel, were studied employing scanning electron microscopy (SEM), isothermal nitrogen adsorption-desorption, calorimetry (DSC) and broadband dielectric spectroscopy (BDS) techniques. The initial Stober particles (specific surface area S-BET similar to 240 m(2)/g) form a quite loose silica network with mainly textural pores of similar to 12 nm in size. Fumed silica (S-BET similar to 260 m(2)/g) demonstrates denser aggregation and increased textural porosity (similar to 11 nm), while silica gel (S-BET similar to 850 m(2)/g) exhibits tremendous intraparticle porosity (tubular-like pores of similar to 6 nm). On adsorption of PDMS (at similar to 20 and similar to 30 wt%), the glass transition temperature (T-g) decreases as compared to the bulk, while the glass transition step broadens. Results suggest loosened molecular packing of the polymer chains accompanied by a broadening of the range of relaxation times in the composites as compared to the neat polymer. On the other hand, the heat capacity step at glass transition is significantly suppressed in the composites, suggesting the formation of a rigid polymer fraction (RAF) at the interfaces with nanoparticles due to strong physical interaction (hydrogen bonding). RAF increases in the order Stober < fumed (A300) < silica gel, this increase following that of S-BET. in agreement with results in previous work on silica/PDMS systems. Next to the segmental dynamics (alpha relaxation) of the bulk-like polymer related to the glass transition, BDS allowed the detection of a separate segmental-like relaxation of the polymer in the interfacial silica-PDMS zone. In terms of timescale the interfacial relaxation is almost identical for Stober and A300, and slightly faster for silica gel. Comparison of the results of the present work with previous results obtained with similar nanocomposites based on low molecular weight PDMS and silica, provides additional support to recently proposed 'S-BET-interfacial dynamics' and 'chain packing-polymer dynamics' correlations. (C) 2018 Elsevier Ltd. All rights reserved.