Hyperbranched polyethoxysiloxane (HPEOS) is suggested as an adsorption-active medium in the crazing of commercial polypropylene film and as a precursor of silica. As a result of delocalized crazing of polypropylene, the nanoporous materials characterized by the effective volume porosity to 60 vol % are received. The reaction of HPEOS hydrolysis into pores of a polymer at the presence of acidic and basic catalysts is studied. Obtained silica phase is shown to stabilize the nanoporous structure of crazed polypropylene. The morphology of polymer/silicate composite is fully determined by the structure of crazed polymer matrices, and it is a system of organic/inorganic interpenetrative nets. Because of this structure, the tensile modulus of the composite material exceeds the modulus of the initial polymer by 50-100%.