ИСТИНА

Solvent crazing is an approach to nanoporous polymer membrane preparation. Additionally, in crazing the polymer matrices can be loaded by different organic and inorganic substances and composites with high mutual dispersity of components can be prepared. Hybrid materials with uniform and layer filler disposition within/on the matrices were obtained by changing the structure of a crazed polymer and a way of filler introduction [1]. In this work two methods of polymer/silica nanocomposite preparation based on the commercial films of isotactic PP, HDPE and PET were described. The first method is to directly introduce silica particles by crazing of a polymer in the tetrahydrofuran solution of silica sol with concentration of 3-4 wt.%. Silica sol is nanogel obtained by intramolecular polycyclization of hyperbranched polyethoxysiloxane, HPEOS. Silica separation within the polymer matrices is the result of the solvent evaporation. The content of introduced silica into a polymer is found to be 10-13 wt.%. The microscopic investigation of obtained samples showed that silica phase, basically, is localized onto polymer film surface as a layer with width of 1.5-2 m. In the volume of a polymer matrices SiO2 particles with a diameter of 5-15 nm are uniformly distributed. The second method is to synthesize silica via hydrolytic polycondensation of ethyl silicate within pores of crazed polymer [2]. HPEOS, its mixtures with isopropanol and tetraethoxysilane, TEOS are used as crazing liquids and silica precursors. Then hydrolytic polycondensation of precursors in the presence of an acid (in steam of 10% water solution of HCl) and basic (in steam of 10% water solution of NH3) catalysts was carried out in polymer matrices at room temperature and isometric condition. The amount of filler in polymeric matrix does differ considerably depending on a type of precursor and varies from 5 to 35 wt.%. The dispersity of silica particles and composite morphology depend on a type of a polymer and precursor and hydrolysis conditions. When HPEOS is used as precursor the composite material consists of two interpenetrating networks: polymer network consisting of oriented fibrils with a diameter of 6-8 nm and silica. The structure of composite materials obtained from TEOS and HPEOS mixtures with isopropanol is different. The main part of silica-gel turns out to be concentrated on a specimen’s surfaces, forming a continuous layer. Spherical nanoparticles with a diameter of 5-150 that are discretely spread in the matrix can be found in a specimen’s volume.