The paper presents comprehensive research results on the possibility of using hydrophobic materials with a developed surface (methylsilica, polymethylsiloxane) as a component of composite systems for biomedical or biotechnological purposes. The mechanisms of their interaction with water depending on the amount of adsorbed water and the presence of additives of liquid hydrophobic substances have been studied.
It has been found that using the wetting-drying procedure («wetting-drying») it is possible to change the bulk density in a wide range and to regulate the volume of meso- and macropores of hydrophilic silica. Hydraulic compaction combined with mechanical loads can be used for transfer to the aqueous medium of hydrophobic silica or other hydrophobic powders (polymethylsiloxane, mixtures of hydrophilic and hydrophobic materials). It was found that the content of bound water in the interparticle gaps of hydrated hydrophobic silica AM-1-300 can reach 1 g/g, and the interfacial energy of water is slightly higher than for hydrophilic silica. In this case, the water adsorbed in the hydrophobic silica is in an nonequilibrium state and is easily replaced by hydrophobic agents (in particular d-chloroform) where 10 % of water passes into a weakly associated state, which is characterized by a small chemical shift.
It is established that the production of composite A-300/AM-1-300 allows to increase the binding energy of water seven times, which occurs due to the predominant formation in the composite system of mainly small clusters of adsorbed water. However, after relatively small mechanical loads, this composite is transformed into a compact material in which both silica components are wetted with water, which acts as a dispersion medium. The binding energy of water is reduced tenfold and becomes less than for the original silica A-300. The reason is the displacement of air from the interparticle gaps. That is, dosed mechanical loads serve as an effective method of controlling the properties of composite systems by transforming the system "solid/water/air" into a system "solid/water".
It is shown that in the interparticle gaps of nanosilica A-300 and its mixtures with AM-1 water and methane can form supramolecular systems that increase the total amount of adsorbed methane to 38 mg/g. It is assumed that the decrease in the signal intensity of adsorbed methane in the NMR spectra with decreasing temperature is due to its partial transition to the solid clathrate state.
Thus, the use of hydrophobic materials as additives to hydrophilic silica or bionanocomposites based on it makes it possible to create new functionalized materials in which, under the influence of hydrophobic-hydrophilic interactions, a supramolecular system is formed, consisting of ordered hydrophobic regions (microcoagulation) and a system of clusters located in interparticle gaps water. Such a system is nonequilibrium and sensitive to external influences, which makes it possible to purposefully change its thixotropic properties, phase state, adsorption-desorption characteristics, etc.
Hydrosil wetting-drying silica (TU U 20.1-3291669-015:2016) was created and implemented, on the basis of which «Polysorbplus» enterosorbent (TU U 10.8-03291669-001:2017) was made, suitable for cleansing the body of toxins of various etiologies. A technological scheme for the production of hydrogenated silica, suitable for use as an enterosorbent and mineral component of biocomposite systems based on medicinal plants, has been developed. Permission documentation has been obtained for the use of the created composites as biologically active additives, effective in the treatment of diseases of the gastrointestinal tract, nervous system, liver, etc. such as "Lymphosilica" (TU U 10.8-03291669-005: 2017), "Sedasil".
Improved protective and stimulating composition of composite systems based on methyl silica and complex fertilizers containing macro- and microelements, registered under the trademark "Ecostim" (TU U 20.2-03291669-021:2013), and fertilizer for pre-sowing treatment of plant seeds , which additionally contains vitamins, biostimulants, bacterial cultures "Defsit" (TU U 20.2-03291669-005:2018). Their use increases the yield of vegetable and cereal crops by 10-20%.
New composite systems based on mixtures of hydrophobic and hydrophilic silica and microbial cultures have been developed and their destruction of water-polluting hydrocarbons has been tested in model studies. It is shown that the film of the contaminant disappears in 50-65 days. The scientific basis for creation of adsorption accumulators of methane based on formation of clathrate structures at a pressure of ~ 1 bar and temperatures of 210-290 K is developed.
Keywords: hydrophobic and hydrophilic dispersed silica, polymethylsiloxane, composite systems, biologically active substances, vegetable raw materials, water, interphase interactions
