Synthesis of new siloxane or sulfur containing symmetrical monomers based on carvone

Abstract

We demonstrated, that based on carvone, new symmetrical AA-type monomers with double bonds can be easily prepared by thiol-ene or Michael addition of dithiols. Moreover, hydrosilylation reaction with difunctional telehelic siloxane, containing Si-H groups was also studied. Obtained monomers are suitable for further polymerization by thiol-ene or hydrosilylation polyaddition.     

Thermodynamic properties of carbosilane dendrimers of the seventh and ninth generations with terminal butyl groups in the temperature range from <Emphasis Type="Italic">T</Emphasis> → 0 to 600 K

Temperature dependences of the heat capacity of carbosilane dendrimers with butyl terminal groups of the seventh and ninth generations were determined in the temperature range from 6 to 600 K by precision adiabatic vacuum calorimetry and differential scanning (dynamic) calorimetry. The physical transitions were revealed and their thermodynamic characteristics were analyzed. The experimental data obtained were used to calculate the standard thermodynamic functions C _p (T), H°(T) − H°(0), S°(T), and G°(T) − H°(0) for the temperature range from T → 0 to 600 K. The thermodynamic function-molar weight isotherms for the dendrimers of the third–ninth generations with terminal butyl groups in the glassy and highly elastic state are linear. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1924–1928, October, 2007.     

Synthesis and modification of polysilylcarbodiimides

Conditions for the synthesis of linear polysilylcarbodiimides based on bis(trimethylsilyl)carbodiimide have been investigated. The method of preparing new silylcarbodiimidesilazane polymers via the polycondensation of bis(trimethylsilyl)carbodiimide with methylphenyldichlorosilane and cyclosilazanes has been developed. The highest molecular mass of the polymers achieves 10 000, as evidenced by GPC measurements. The structure of polysilylcarbodiimidesilazanes has been examined by IR spectroscopy and ¹H NMR studies. Silazane units are incorporated into polymer chains as linear and stressed cyclodisilazane fragments. TGA experiments have revealed that silazane fragments reduce weight losses of the new polymers in the course of thermal degradation.     

Protolytic properties of flavonols from pea chloroplasts

Using the buffer capacity method, a study has been made of the protolytic properties of three flavonoids isolated from pea chloroplasts: kaempferol 3-D-triglucoside (KG), kaempferol 3-D-triglucoside p-coumarate (KGC), and quercetin 3-D-triglucoside p-coumarate (QGC). It has been shown that the curves of the buffer capacities of solutions of the flavonoid investigated have from two to four peaks of dissociation constants. When the substances participate in photobiochemical reactions, they are capable of manifesting protonophoric properties.Institute of Photosynthesis, Academy of Sciences of the USSR, Pushchino. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 337–340, May–June, 1980.     

Organosilicon compounds in supercritical carbon dioxide: Synthesis,polymerization, modification,and production of new materials

The main promising opportunities for the advantageous combination of organosilicon compounds and supercritical carbon dioxide both as a solvent and as a reagent in chemical processes are analyzed. The main processes of polymerization and modification of polymer matrices that are performed in supercritical СО₂ with the use of organosilicon materials of various types are outlined. Methods for the obtaining organosilicon polymers and polymer-inorganic composites and methods for the application of siloxane stabilizers in the dispersion polymerization of monomers in supercritical СО₂ are described. Studies of the insertion of a СО₂ molecule into Si–H, Si–N, and Si–O–Me bonds in reactions that feature exceptionally high chemical selectivity and afford a wide spectrum of products potentially useful for application in the chemistry of polymer materials are considered. It is shown that the silylation of surfaces of various types and morphologies in the medium of supercritical СО₂ is a rapidly developing green approach that makes it possible to obtain highly uniform defect-free coatings with variable desired functionality.     

Hydrolytic polycondensation of methylalkoxysilanes under pressure

Hydrolytic polycondensation of methytrialkoxysilanes under the pressure in water and in carbonic acid was investigated. It is shown, that both processes proceed with full conversion of the monomer to form a low molecular soluble polymethylsilsesquioxanes. However, they have a different structure: in water branched compounds were produced and in carboxylic acid polycyclic compounds were synthesized. A type of alkoxy group affects the course of the process. In the case of hydrolytic polycondensation of methyltriethoxysilane under the pressure, unlike methyltrimethoxysilane, full conversion is observed only when additional homogenization of the reaction mixture takes place by vigorous stirring or increasing temperature of the process.

     

Small-angle x-ray scattering study of polymer structure: Carbosilane dendrimers in hexane solution

The three-dimensional organization of monodisperse hyper-branched macromolecules of regular structure—carbosilane dendrimers of zero, third, and sixth generations—has been studied by small-angle X-ray scattering (SAXS) in solution. The use of modern methods of SAXS data interpretation, including ab initio modeling, has made it possible to determine the internal architecture of the dendrimers in dependence of the generation number and the number of cyclosiloxane end groups (forming the shell of dendritic macromolecules) and show dendrimers to be spherical. The structural results give grounds to consider carbosilane dendrimers promising objects for forming crystals with subsequent structural analysis and determining their structure with high resolution, as well as for designing new materials to be used in various dendrimer-based technological applications.     

Facile synthesis and optical properties of bithiophenesilane monodendrons and dendrimers

Three generations of bithiophenesilane monodendrons and dendrimers consisting of 3-45 2,2'-bithiene-5,5'-diyl units were synthesized by means of effective coupling reactions between the corresponding bithienyllithium derivatives and chlorosilanes. These compounds show efficient photoluminescence in the violet-blue region, the quantum yield of which is 5-15 times higher than that for the parent bithiophene or bithiophenesilanes.