Thioether-Containing Zirconium(Alkoxy)Siloxanes: Synthesis and Study of Dielectric and Mechanical Properties of Silica-Filled Polydimethylsiloxane Compositions Cured by Them.

A number of thioether-containing zirconium siloxanes, differing in their composition and metal atom shielding degree with a siloxy substituent, were synthesized and characterized. Synthesis of such compounds made it possible to evaluate the effect of sulfur atoms' presence in the cured compositions on their dielectric properties, as well as to evaluate their curing ability and influence on mechanical characteristics compared to the sulfur-free analogs obtained earlier. Studying a wide range of compositions differing in their content and ratio of metallosiloxane and silica components revealed that such systems are still typical dielectrics. At the same time, the introduction of thioether groups can provide increased dielectric constant and conductivity in comparison with previously obtained sulfur-free similar compositions in the <102 Hz frequency range (dielectric constant up to ~10-30 at frequency range 1-10 Hz). As before, the dielectric parameters increase is directly determined by the silica component proportion in the cured material. It is also shown that varying sulfur-containing zirconium siloxanes structure and functionality and its combination with previously obtained sulfur-free analogs, along with varying the functionality and rubber chain length, can be an effective tool for changing the dielectric and mechanical material parameters in a wide range (tensile strength 0.5-7 Mpa, elastic deformation 2-300%), which determine the prospects for the use of such cured systems as dielectric elastomers for various purposes.

Nanostructured organosilicon luminophores and their application in highly efficient plastic scintillators.

Organic luminophores are widely used in various optoelectronic devices, which serve for photonics, nuclear and particle physics, quantum electronics, medical diagnostics and many other fields of science and technology. Improving their spectral-luminescent characteristics for particular technical requirements of the devices is a challenging task. Here we show a new concept to universal solution of this problem by creation of nanostructured organosilicon luminophores (NOLs), which are a particular type of dendritic molecular antennas. They combine the best properties of organic luminophores and inorganic quantum dots: high absorption cross-section, excellent photoluminescence quantum yield, fast luminescence decay time and good processability. A NOL consists of two types of covalently bonded via silicon atoms organic luminophores with efficient Förster energy transfer between them. Using NOLs in plastic scintillators, widely utilized for radiation detection and in elementary particles discoveries, led to a breakthrough in their efficiency, which combines both high light output and fast decay time. Moreover, for the first time plastic scintillators, which emit light in the desired wavelength region ranging from 370 to 700 nm, have been created. We anticipate further applications of NOLs as working elements of pulsed dye lasers in photonics, optoelectronics and as fluorescent labels in biology and medical diagnostics.