AbstractPolydimethylsiloxane (PDMS) colloidal silica composites prepared with the use of the dispersion of colloidal silica (CS) of similar particle size and distribution in different mediums/solvents are investigated for their rheological, thermal, and mechanical properties. Regardless of the dispersion medium of CS, thermal analysis showed the increased thermal stability of PDMS with the addition of CS. The rheological analysis showed that the composites prepared from CS dispersed in isopropanol (IPA) and CS dispersed in methylethylketone (MEK) showed significant enhancement in viscosity at higher loadings as compare with the composite prepared from the CS dispersed in water and methanol indicating more Filler–polymer interactions. Similarly, the tensile stress–strain curves, hardness, and tear strength displayed significant improvement with PDMS‐CS‐MEK and PDMS‐CS‐IPA composites. The results of this study not only provide the insights of solid–liquid–liquid interface leading to different extent of polymer‐filler interaction, there by the bulk properties, it also helps to minimize the surface treatment steps while preparing the composites. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012