ИСТИНА

Currently, research is being conducted intensively associated with the possibility of synthesizing artificial biologically active forms of porous calcium phosphates, which are analogous to the mineral component of bone tissue. A method for obtaining porous CPs using template synthesis in nanoporous polyolefin matrices is proposed in this paper. Porous structure of polymer films with an average pore diameter of 5-20 nm is formed according to the crazing mechanism. When the matrix is removed by dissolution or burning, an introduced inorganic substance forms a porous solid residue. As objects for study, we used commercial films of isotactic polypropylene and high-density polyethylene. The creation of a porous structure in polymer films was carried out by crazing during uniaxial tension in the presence of liquid (isopropanol, n-heptane) or supercritical (SC-CO2) media. CPs were obtained within the pores’ volume of a polymer by an exchange reaction between aqueous solutions of Ca(NO3)2 and (NH4)2HPO4 at pH=5-9 and a room condition, using the countercurrent diffusion method. The content of CPs was about 20-30 wt.% and the average crystallite size was 10-40 nm. It was found by SEM that CP particles were localized only in crazes. Removal of the polymer matrix from composites by heating in air at a temperature of 500°C made it possible to obtain porous residues of CPs consisting of particles of different morphology. The particles synthesized in the PP matrix were layered needle-like crystals with a length of 100-150 nm and a diameter of about 10 nm. The thickness of each layer was about 0.7 nm and the distance between the layers was 1.2 nm. Heating the composites based on the HDPE or annealed PP matrix allowed us to prepare a porous CP plate with a thickness of about 15-20 μm, consisting of spherical particles with 50-90 nm in diameter. The pore diameter of the similar residues was varied from 50 nm to several microns. Thus, the proposed approach of the template synthesis of calcium phosphates in porous polymer films obtained via crazing allowed us to directionally regulate their porosity and structure. It is important to build bone implants with optimal properties. This study was financially supported by the Russian Science Foundation (project no. 17-13-01017).