In this work, a new simple and robust method for preparation of polymer-grafted inorganic hybrids through “grafting to” reaction is presented. Polymer chains were synthesized by reversible chain transfer catalyzed polymerization (RTCP) are capped with iodine according to the RTCP mechanism. The obtained iodine-capped polymer chains can react irreversibly with the hydroxyl groups available on the surface of inorganic materials through a nucleophilic substitution (SN) reaction. In this method, there is no need to modify the surface of inorganic materials or to functionalize polymer chains prior to the “grafting to” reaction. RTCP produced polystyrenes with different molecular weights, e.g., 4,000, 6,000, and 8,000 g/mol, and silica nanoparticles were employed as the polymer and inorganic materials, respectively. The resulting hybrids were characterized by Fourier transform infrared spectroscopy, thermal gravimetric analysis, and transmission electron microscopy techniques. According to the results, graft density decreased by increasing the polystyrene molecular weight. Additionally, the rheological studies of prepared polystyrene nanocomposites containing 2 wt % of the produced hybrids confirmed the better dispersion of the modified hybrids in the polystyrene matrix. The glass transition temperature (T g) of the polystyrene nanocomposites was driven by differential scanning calorimeter technique. Analysis of nanocomposites’ T g results revealed that increment of the grafted polymer molecular weight of hybrids increased the glass transition temperature of the prepared nanocomposites due to improvement of the dispersion level.