ИСТИНА

We will consider an alternative approach, which involves in situ synthesis of nanoparticles within the solvent-crazed porous matrices, based on glassy and semi-crystalline polymers. The porous polymeric membranes obtained via solvent crazing (transition of glassy and semi-crystalline polymers in highly dispersed and oriented state upon uniaxial stretching in presence of adsorptionally active media is referred to as solvent crazing) are attractive as templated matrices. The development of nanometric pores allows one to apply them as microreactor for various chemical reactions (reduction, exchange, etc.). This approach makes possible to solve several fundamental problems: stabilization of nanoparticles due to the limiting action of walls and mutual dispersion of thermodynamically incompatible components. The objective of this work is to demonstrate the possibilities of the application of various porous polymer matrices prepared via solvent crazing as microreactors for the synthesis and stabilization of metallic nanoparticles with a desired level of dispersion and morphology. The initial materials for obtaining porous polymer matrices and composites were commercial films of isotropic high density, isotropic isotactic polypropylene, amorphous poly(ethylene terephthalate), amorphous poly(vinyl chloride). 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 Cu, Ni, Co, Ag particles as a result of chemical reduction from the salts using various reducing agents such as sodium boron hydride, hydrazine or by thermal reduction was studied. 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 as presented in the Figure. 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; aggregates have a preferential orientation along fibrils. 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.