Nanocomposites Based on Porous Polylactide, Obtained by Crazing Mechanism in Water–Ethanol Solutions, and Calcium Phosphates
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Systematic investigations of uniaxial deformation of an amorphous isotropic polylactide film in water–ethanol solutions of different composition are carried out and optimal conditions for polymer deformation by the crazing mechanism are determined. In the whole range of the solution compositions, the polylactide deformation is accompanied by the formation of a highly dispersed fibrillar-porous structure according to the mechanism of classical crazing. When the ethanol content is ~35 wt %, the film deformability increases sharply, and it reaches 400–500% in solutions with the ethanol content of more than 45 wt %. The fine structure of the polylactide crazes during deformation in a 50% aqueous ethanol solution is studied in situ by X-ray scattering at small angles. The intensity distribution curves for polylactide samples, regardless of the degree of deformation, are characterized by the presence of an interference maximum, which indicates the regular arrangement of the individual fibrils in crazes relative to each other. The interfibrillar distance is 40 nm at the degree of deformation up to 200%. Composite materials containing nanoparticles (average crystallite size is ~30 nm) of various biologically active calcium phosphates are obtained on the basis of porous polylactide matrices (with a volumetric porosity of ~45 vol %) using the method of countercurrent diffusion between aqueous solutions of calcium nitrate and ammonium hydrogen phosphate. The filler content has reached 30 wt %. Such organomineral materials are considered promising in the field of biomedicine.
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