V. V. Kazantseva

Nanocomposites Based on Epoxy Resin and Silicon Dioxide Particles

The cure of an epoxy resin (3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate) in the presence of silica nanoparticles modified by 3-(triethoxysilyl)propylsuccinic anhydride has been studied. Optimal conditions for the preparation of optically transparent polymer nanocomposites with increased glass transition temperatures are determined. The glass transition temperatures of the above nanocomposites are 50–70°C higher than those of the unfilled epoxy resin synthesized under the same conditions (100°C).

Chemical transformations of poly(arylene ether ketones) containing side functional groups

Conditions for chemical transformations of poly(arylene ether ketones) containing side carboxyl and phthalimidine functional groups have been investigated. The reason why the chemical modification of poly(arylene ether ketones) with side acid chloride groups leads in some cases to the formation of insoluble products is established. Ionogenic and comb-shaped poly(arylene ether ketones) with hydrophobic fragments in side branches are obtained through chemical transformations of previously synthesized polymers containing side carboxyl, hydroxyl (alcohol), and phthalimidine groups. The properties of poly(arylene ether ketones) can be varied in a wide range via chemical reactions of side reactive groups.

Comb-shaped homo- and copoly(arylene ether ketones) containing hydrophilic groups in side chains

Comb-shaped poly(arylene ether ketones) containing hydrophilic fragments in side chains are synthesized through the interaction of side reactive carboxyl groups of poly(arylene ether ketones) with methyl ethers of poly(ethylene glycol). Films based on these polymers possess tensile strengths up to 89 MPa and relative elongations at break up to 340%. Comb-shaped poly(arylene ether ketones) swell in water, and some of them show solubility in ethanol and methanol.

Synthesis of amorphous block copoly(arylene ether ketones) and their characterization

Exchange reactions that may proceed in the course of polycondensation during formation of a polymer from 4,4′-difluorobenzophenone and 4,4′-(isopropylidene)diphenol have been studied. It has been shown that the molecular mass of the polymer decreases under the action of 4,4′-(isopropylidene)diphenol diphenolate. The nucleophilic substitution of the activated aryl halide in DMAA in the presence of potassium carbonate yields high-molecular-mass block copoly(arylene ether ketones) based on 4,4′-difluorobenzophenone and a number of bisphenols. It was demonstrated the synthetic procedure and the chemical structure of block copoly(arylene ether ketones) strongly affect the onset temperature of softening and the mechanical characteristics of the films based on these polymers.

Effects of the phases and the sizes of disperse particles on the elastic moduli of composites based on polymer mixtures

Different methods of calculating the elastic moduli of materials based on incompatible polymer mixtures are analyzed. These materials comprise fine dispersions of one of the polymers in a polymer matrix of another polymer. Different variants were analyzed: a dispersion of a solid polymer in an elastomer, where solid dispersion particles chemically react with the elastomer, or do not chemically interact with the elastomer matrix; a dispersion of a solid amorphous polymer of a particular chemical structure in a solid amorphous matrix of a polymer having a different chemical structure; and a dispersion of a partially crystalline polymer in a solid amorphous polymer. The dependence of the elastic moduli on the molar and volume fractions are defined by the van der Waals volumes of the components, the molecular masses of the repeating units, the densities of the components, the domain volumes, etc. These dependences are associated with the physical states and the phases (a rubber polymer, a crystalline polymer, or a solid amorphous polymer) of the mixed components.

Synthesis and approaches to the synthesis of phthalide-containing block-copolymers combining poly(arylene ether ketone) blocks with polymer blocks of different classes

223 Poly(arylene ether ketone)s (PAEKs) due to a combination of excellent mechanical and thermal properties [1, 2] are widely used in industry as high strength heat resistant and thermally and chemically stable structural thermoplastics. Among them, phtha lide containing PAEKs stand out by enhanced heat resistance and unique impact elasticity [3]. Further more, such PAEKs show unusual properties promising for electronics, including the electronic switching effect under external action (for example, pressure, electric fields, etc.) [4], previously revealed for poly(diphenylenephthalide) [5]. By the example of phthalide containing PAEKs, it was shown that the structure inhomogeneity of copolymers and block copolymers of this class provides a sharp amplification of these new unusual electrophysical properties [6] typical for phthalide containing homo PAEKs. For that reason, it was expedient to develop such an approach and increase the extent of inhomogeneity of phthalide containing block copolymers by combining the blocks of polymers of different classes. Therefore, the aim of this work is to search for ways to produce phthalide containing block copolymers combining the blocks of polymers of different classes, especially polyarylates (PAr) and PAEKs.

Analysis of stress relaxation in the nonlinear region of mechanical behavior

The principles defining the relaxation parameters of polymers in the nonlinear region of mechanical behavior are considered. This definition involves relaxation kernels, which are based on the analysis of changes in the thermodynamic functions in the course of the relaxation process. At high strains corresponding to nonlinear mechanical behavior, an excess free volume arises, the rate constant of interaction between relaxants becomes dependent on the mechanical stress, and nonlinear mechanical behavior comes into play. With allowance for this factor, the temperature dependence of rate constants of interaction involves the dependence of the activation energy of relaxation on the mechanical stress. This modified equation allows a correct description of stress relaxation and makes it possible to estimate an important physical parameter: the excess free volume, in which the elementary event of relaxation process takes place. Computer software is written for the approximation of stress relaxation curves in the linear and nonlinear regions of mechanical behavior and for the estimation of the relaxation parameters of the materials.