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Department of Physical Chemistry of Fossil Fuels L.M. Lytvynenko Institute of Physical Organic Chemistry and Coal Chemistry of NAS of Ukraine
Department of Physical Chemistry of Fossil Fuels L.M. Lytvynenko Institute of Physical Organic Chemistry and Coal Chemistry of NAS of Ukraine
L. M. Litvinenko Institute of Physical-Organic Chemistry and Coal Chemistry
Department of Physical Chemistry of Fossil Fuels L.M. Lytvynenko Institute of Physical Organic Chemistry and Coal Chemistry of NAS of Ukraine

One of the promising directions for production of advanced materials is creation of hybrid organic-inorganic nanocomposites that demonstrate not only the improved properties of organic matrix, but also the emergence of the new specific properties due to the presence of inorganic component. Hybrid organic-inorganic materials can be synthesized by sol-gel method as a result of sol-gel process involving organic-inorganic precursors. Nowadays sol-gel technique is considered as a simple and an ecologically friendly method of nanocomposite syntheses.

         The article is devoted to research of the rheological behavior of sol-gel systems on the basis of two organic-inorganic precursors – tetraethoxysilane (TEOS) and 3-methacryloxypropyltrimethoxysilane (MAPTMS). Dynamics of structure formation in these sol-gel systems was studied by viscometric method using RHEOTEST 2.1. The study of the viscosity of sol-gel systems with different ratio of MAPTMS / TEOS allowed to determine the effect of temperature, system composition, concentration of sol-gel process catalyst on the time of reaching the percolation threshold when gelation takes place.

          By the temperature dependence of the time of reaching the percolation point in the studied systems, the activation energy of gelation process was determined.

          Since it is known that MAPTMS hydrolysis and condensation reactions during sol-gel process occurs with a low rate, which may be explained by steric effect due to the presence of acrylate fragment in MAPTMS structure, this precursor was combined with the widespread precursor TEOS having a higher rate of sol-gel transformation. It was established that the replacement of the part of TEOS by MAPTMS slows down the gelation process under the given conditions.

          Studying of the gradient dependence of the viscosity of sol-gel systems allowed to determine the frictional ηo and elastic ηs components of the viscosity of sol-gel systems, depending on temperature and the initial system composition.

          The obtained results are of practical importance for the synthesis of organic-inorganic composites using sol-gel process, since they allow to find the appropriate ratio of precursors and the conditions for sol-gel transformation.

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