E. V. Getmanova

Rheology of carbosilane dendrimers with various types of end groups

The rheological properties of high-generation carbosilane dendrimers carrying different kinds of terminal groups are studied. It is shown that the nonlinear viscoelastic behavior of dendrimers and the high-temperature relaxation transition in dendrimers are interrelated and result from the reversible breakdown of the supramolecular structure formed by the system of contacts of exterior shells of dendrimers. The strength of the supramolecular structure is dependent on the specific interaction of terminal groups of dendrimers and their mobility. The dendrimers under study demonstrate the dualism of macromolecule-particle properties: They behave as both polymer melts and colloidal systems.

Electrical properties of composites based on polystyrene with hybrid silicon dioxide particles

Composites based on polysterene and hybrid core-shell nanoparticles are studied; the nanoparticle core consists of silicon dioxide, and ethylphenylic groups (organic shell) are grafted to the core surface. It is shown that the permittivity, the volume resistivity, the thermostimulated depolarization current spectra, and the glass transition temperature of these materials depend on the nanofiller content and, what is more important, the nanofiller distribution over the polymer volume in the form of particles or their aggregates.

Behavior of polystyrene-based nano- and microcomposites under fast compression

Composites based on polystyrene (PS) and core-shell hybrid nanoparticles of molecular silica sol are studied during fast compression. At a certain critical pressure, PS and the related composites are found to fail instantaneously. This process is accompanied by the emission of electromagnetic and acoustic waves. The sample composition and the filler particle size change both the critical pressure during explosion and the frequency characteristics of the appearing electromagnetic and acoustic waves. The fracture of PS and the related composites is accompanied by the formation of a fibrillar structure.

Rheological properties of sulfur-containing hyperbranched polycarbosilanes and related magnetic compositions

The rheological properties of hyperbranched polycarbosilanes with butyl and decyl terminal groups and their sulfur-containing analogs were compared. The use of various sulfurcontaining precursors made it possible to control both the total sulfur content and the position of sulfur atoms in the molecular structure. The magnetic compositions based on sulfur-containing hyperbranched polycarbosilanes were prepared for the first time, and the influence of the external magnetic field intensity on their rheological properties was studied. The introduction of the sulfur atom improves the stability of the magnetic composition, while their magnetorheological response remains unchanged.

Synthesis of thioether-containing carbosilane dendrimers with sterically shielded sulfur atoms

Carbosilane thiols were synthesized as the first- and second-generation (in silicon) dendrons. It was demonstrated that the resulting bulky thiols successfully undergo the thiol—ene addition to third-generation polyallyl carbosilane dendrimer as a photoinitiated radical reaction to give the corresponding thioether-containing derivatives with sterically shielded sulfur atoms.

Fracture of polystyrene- and molecular silica sol-based nanocomposites during fast compression

Polystyrene-based composites containing hybrid molecular silica sol nanoparticles with a core-shell structure are studied during fast compression. Polystyrene and the related composites are found to fail instantaneously at a certain critical pressure, which is accompanied by the emission of electromagnetic and acoustic waves. The composite composition changes the critical pressure during explosion and the frequency characteristics of the generated electromagnetic and acoustic waves. The charge density transfer mechanism in a composite with a filler concentration higher than 10 wt % is shown to differ from that in composites with a lower filler content.