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Epoxy/silica thermosets with tunable matrix (vitrimers) were prepared by thermal curing of diglycidyl ether of bisphenol A (DGEBA) in the presence of a hardener—4-methylhexahydrophthalic anhydride (MHHPA), a transesterification catalyst—zinc acetylacetonate (ZAA), and 10–15 nm spherical silica nanoparticles. The properties of the resulting material were studied by tensile testing, thermomechanical and dynamic mechanical analysis. It is shown that at room temperature the introduction of 5–10 wt% of silica nanoparticles in the vitrimer matrix strengthens the material leading to the increase of the elastic modulus by 44% and the tensile stress by 25%. Simultaneously, nanoparticles enhance the dimensional stability of the material since they reduce the coefficient of thermal expansion. At the same time, the transesterification catalyst provides the thermoset with the welding ability at heating, when the chain exchange reactions are accelerated. For the first time, it was shown that the silica nanoparticles strengthen welding joints in vitrimers, which is extremely important, since it allows to repeatedly use products made of thermosets and heal defects in them. Such materials hold great promise for use in durable protective coatings, adhesives, sealants and many other applications.

Data on gradient polymeric materials that possess broadly varying mechanical, optical, and other properties are generalized. The term "gradient materials of the first type" refers to materials that possess a gradually variable elasticity modulus in the range of 3-2000 MPa for the same material that possesses no layers or interfaces, pasting, heat sealing, etc. They are produced as either transpar ent molds or composites with various reinforced fillers. The synthesis of these materials is based on the formation of polymer networks containing bulky cross linked points with short flexible fragments linking them. These networks have been computer simulated using the physical approach developed by the authors and the chosen software, which allows one to calculate polymer properties based on their chemical structure and the implementation of computerized synthesis of polymers with pre scribed properties. The term "gradient materials of the second type" refers to materials with abruptly changing elasticity modulus and transition zone between the glassy and the rubbery states. GRADIENT POLYMERIC MATERIALS 109 pound. Since the search for such a structure is one of the objectives of this method, consistent description of structures in the method of atomic constants and in CPOS must be provided. The table of atoms and the table of relatedness that sets the selection of atoms and types of bonds in the compound structure are fundamental for CPOS software. The application of this method induces the suit ability of forming these tables for every processed formula of the repeating unit. The problem of the user's communication with the software is of special interest. The image of the structure represents a planar dis position of atoms linked by definite types of bonds. If necessary, correspondence to linear Wiswesser for mulas [10] or Morgan's record form [11] is set using tables of atoms or relatedness. The problem of unique interpretation of the repeating unit structure indicated on the display is of importance. For this purpose, the presence of information about atoms, groups of atoms, and bonds in the database is monitored by the program. The program is compatible with Windows 95 or more recent versions.The Cascade program allows one to calculate more than 60 properties of polymers and copolymers. The most fundamental properties in accordance with the review are the van der Waals volume, Hildebrand solubility parameter, surface energy, refractive index at room temperature, dielectric constant at room temperature, glass transition temperature, dependence of glass transition temperature on molecular mass, temperature of onset of intensive thermal degradation, interface tension at the polymer-polymer boundary, and the elasticity modulus of rubber (rubber like plateau).The software enables one to calculate the properties of copolymers, homogeneous mixtures of poly mers, etc. The Cascade program enables the calculation of 16 characteristics for low molecular weight organic liquids. Calculation of Elasticity Modulus for Polyme...

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