Molecular forms of silica based on polyethoxysiloxane, silicasol, and tetraethoxysilane, being prospective fillers for polymer nanocomposites were prepared and studied thoroughly by gel permeation chromatography (GPC), viscometry, dynamic light scattering (DLS), thermomechanics, and wide angle X-ray scattering (WAXS). All synthesized objects were shown to possess the structure of "core-shell'" type. Particle radius varies in a range of 0.5-10 nm. The core structure depends on a method of preparation, while a particle morphology (share of core and shell) may be regulated within every of three methods. (c) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4310-4322, 2010