Aerogel-Like Material Based on PEGylated Hyperbranched Polymethylethoxysiloxane.

Aerogels are a class of materials that have gained increasing attention over the past several decades due to their exceptional physical and chemical properties. These materials are highly porous, with a low density and high surface area, allowing for applications such as insulation, catalysis, and energy storage. However, traditional aerogels, such as pure silica aerogels, suffer from brittleness and fragility, which limit their usefulness in many applications. Herein, we have addressed this problem by using organosilicon compounds, namely polymethylsilsesquioxane derivatives, for the synthesis of aerogel-like materials. Specifically, we have developed a novel approach involving surfactant-free synthesis of microcapsules from partially PEGylated hyperbranched polymethylethoxysiloxane. Due to the highly diphilic nature of these compounds, they readily concentrate at the oil/water interface in aqueous emulsions encapsulating oil droplets. During the subsequent condensation, the organosilicon precursor is consumed for hexane encapsulation (yielding hollow microcapsules) followed by the formation of a continuous condensed phase. Concurrently, methyl groups ensure the hydrophobicity of the resulting materials, which eliminates the need of using additional reagents for their hydrophobization.

Synthesis of Multifunctional Oligomethylsilsesquioxanes by Catalyst-Free Hydrolytic Polycondensation of Methyltrimethoxysilane under Microwave Radiation.

The catalyst-free hydrolytic polycondensation of methyltrimethoxysilane under microwave radiation has been studied. The effect of molar ratios of the reagents (MTMS/H2O = 1/0.5-1/9), radiation power (20-300 W), temperature (30-50 °C) and duration of exposure (2.5-90 min) on the course of the process is considered. It has been shown that the use of microwave radiation promotes the activation of the process, and almost complete conversion of the monomer can be achieved in 5 min at 30 °C, 20 W and an MTMS/H2O ratio of 1/3. The optimal radiation power for the maximum conversion of the monomer and MeO-groups is in the range from 20 to 100 W. An increase in the water amount, the duration and temperature of the process contribute to an increase in the monomer conversion, a decrease in the content of residual MeO-groups and the yield of non-volatile oligomethylsilsesquioxanes. The limits of this approach using to the synthesis of multifunctional branched polyorganosilsesquioxanes are determined. Depending on the process conditions, homogeneous water-alcohol solutions of oligomethylsilsesquioxane with a concentration of 20 to 50 wt.% can be obtained. The OH-group content and the molecular weight of the obtained oligomers vary from 10 to 30 wt.% and from 1000 to 600 Da, respectively.

Chemical Recycling of High-Molecular-Weight Organosilicon Compounds in Supercritical Fluids.

The main known patterns of thermal and/or catalytic destruction of high-molecular-weight organosilicon compounds are considered from the viewpoint of the prospects for processing their wastes. The advantages of using supercritical fluids in plastic recycling are outlined. They are related to a high diffusion rate, efficient extraction of degradation products, the dependence of solvent properties on pressure and temperature, etc. A promising area for further research is described concerning the application of supercritical fluids for processing the wastes of organosilicon macromolecular compounds.