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Recently a great attention has been paid to studying an ever-growing scientific direction referred to as nanotechnology. This direction involves the preparation of various composite materials, e.g. polymer-inorganic hybrid materials, with nanometric level of dispersion of the components. In this work, the solvent-crazed porous polymeric matrices are suggested to be used as the templates for in situ synthesis of nanoparticles of metals (Ni, Cu, Fe), metal oxides and salts (AgCl). Porous matrices of PET, PVC, PP and HDPE were obtained via solvent crazing, i.e. via uniaxial stretching in the presence of adsorptionally active media (isopropyl alcohol). The value of an effective volume porosity of the prepared matrices is 20 – 65 vol.%, the average diameter of pores is 5 – 15 nm. The development of nanometric pores allows one to apply them as microreactors for various chemical reactions (reduction, exchange, etc.). Two main methods of an introduction of the initial reagents in the porous structure are considered, namely during the pores’ formation and via the counter-current diffusion. The structure of a composite material depends on the structure of the initial porous polymer matrices. The mechanism of crystallization of the low-molecular substances in the solvent-crazed polymers is discussed. On the initial stages, the crystallites with a diameter from 10 to 80 nm are formed on the polymer fibrils. Further crystallites aggregate and fibrils are involved in this process. These aggregates with a diameter of 100 – 400 nm can be uniformly distributed in the polymer matrices or can be concentrated as a layer with a thickness of 5 – 40 mcm.