RU2715198C1 - Method of producing macroporous form-stable polymer hydrogels using microwave radiation (embodiments) - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: group of inventions relates to hybrid organo-inorganic materials, specifically to versions of a method of producing a porous form-stable polymer hydrogel. In one embodiment, the hydrogel is obtained by sol-gel technology in the presence of a reaction mixture containing poly-N-vinylamide, tetraethoxysilane (TES), a basic catalyst and an organic solvent, followed by exposure of the above reaction mixture to microwave radiation (MWR). In another embodiment, the non-porous polymer hydrogel obtained by sol-gel technology in the presence of a reaction mixture containing poly-N-vinylamide, thermal power plant and the main catalyst is subjected to swelling in an organic solvent with subsequent exposure of the MWR to the swollen polymer hydrogel.

EFFECT: technical result is providing non-toxic porous form-stable polymer hydrogels based on poly-N-vinylamides, as well as maintaining porosity of said hydrogels during swelling and drying.

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Description

The invention relates to the field of hybrid organo-inorganic materials, to their structural modification, namely, to a porous hydrogel based on poly-N-vinylamides and tetraethoxysilane, as well as to variants of the method for producing it by sol-gel technology under the influence of microwave irradiation.

Classical, well-known methods for the formation of porous systems involve the use of compounds that produce gas during heating or chemical reactions, which leads to foaming of the liquid composition. The porous structure can be formed due to extraction (washing out, burning out) from the molded product, by sintering metal, ceramic or polymer monolithic particles (powders) and porous granules. Low-boiling liquids emit gases as a result of boiling, evaporation, desorption when the temperature rises or when the pressure decreases. Substances emitting gaseous products as a result of thermal decomposition: ammonium salts of mineral and carboxylic acids, bicarbonates and carbonates of alkali metals, emitting NH ₃ and / or CO ₂ , NH ₂ COONH ₄ , NaHCO ₃ , Na ₂ CO ₃ , mixture (NH ₄ ) ₂ CO ₃ ⋅H ₂ O with (NH ₄ ) HCO ₃ ; azo and diazo compounds, N-nitroso compounds, sulfonyl hydrazides, azides, etc. Low-boiling volatile liquids - aromatic, aliphatic and halogen-containing hydrocarbons, alcohols, ethers, ketones [Encyclopedia of Polymers, T. 3. - M., 1977, p. 153-159; Berlin A.A., Shutov F.A. Foam polymers based on reactive oligomers. - M .: Chemistry, 1978, 296 p .; Berlin A.A., Shutov F.A. Chemistry and technology of gas-filled high polymers. - M .: Nauka, 1980, 504 p.].

But all these methods are described for the synthesis of solid porous systems.

In the synthesis of a porous hydrogel, i.e. system, which is a gelatinous body, able to maintain shape, with elasticity and elasticity, but without fluidity, it is necessary to take into account capillary effects that can “tighten” the pores. The spatial network in hydrogels is formed by particles of a dispersed phase, which are interconnected by intermolecular interaction (hydrogen, ionic, covalent forces). Gels can form during coagulation of sols, when the contacts between particles are easily and reversibly destroyed by mechanical and thermal influences (sol-gel transition). There are hydrogels and organogels, where water and organic compounds, respectively, act as a dispersion medium. When drying the gels, depending on the method of removing the dispersion medium, aerogels, ambigels, cryogels and xerogels can be obtained, which differ significantly in density and micromorphology features.

In chemistry and polymer technology, gels are water-swollen ion-exchange resins; spatially cross-linked dextrans (Sephadexes), polyacrylamides, swollen copolymers of styrene and divinylbenzene in liquid hydrocarbons, as well as rubber based on natural and some synthetic rubbers; hydrogels of gelatin, agar, polyvinyl alcohol; organogels of certain cellulose ethers, acrylonitrile. Man is constantly improving a variety of materials, looking for new areas of their application. With good reason, this applies to polymer hydrogels. As it turned out, the register of their studied properties is still far from complete [Grosberg A.Yu., Khokhlov AR Physics in the world of polymers. - M .: Nauka, 1989, 208 p .; Khokhlov A.R. and others. Self-organization in ion-containing polymer systems / Uspekhi Fizicheskikh Nauk, 1997, T. 167, No. 2, p. 113-128; Khokhlov A.R. Susceptible Gels / Soros Educational Journal, 1998, No. 11, p. 138-142; Filippova O.E. "Susceptible" polymer gels / High molecular weight compounds, series C, 2000, T. 42, No. 12, p. 2328-2352; Galaev Yu.V. “Smart” polymers in biotechnology and medicine / Advances in Chemistry, 1995, T. 64, No. 5, p. 505-524; Philippova O.E. et al. Charge-induced Microphase Separation in Polyelectrolyte Hydrogels with Associating Hydrophobic Side Chains: Small-angle Neutron Scattering Study / Langmuir, 2003, V. 19, No. 18, pp. 7240-7248; Shlyakhtin O.A. IUPAC. Compendium of Chemical Terminology. 2nd ed. (the "Gold Book") / Compiled by A.D. McNaught, A. Wilkinson. - Oxford: Blackwell Scientific Publications, 199; Filippova O.E. “Smart” polymer hydrogels / Nature, 2005, No. 8, p. 71-73; Chemical Encyclopedia, T. 1. - M .: Soviet Encyclopedia, 1988, p. 513].

Materials based on polymer hydrogels have been known for almost half a century and are widely used in various fields, including those related to biotechnology, medicine, and agriculture.

To date, hydrogels based on many polymers and their compositions have been prepared. A special place among them is occupied by three-dimensional polymer systems with pores of tens and hundreds of micrometers in size, the so-called macro- and super-porous polymer hydrogels. They are used as components of systems with controlled release of the active substance, materials for implants, and also as substrates for growing cells and tissues in tissue engineering [Hoffman A.S. Hydrogels for biomedical applications / Advanced Drug Delivery reviews, 2002, V. 43, N. 1, pp. 3-12; Drury J.L. et al. Hydrogels for tissue engineering: scaffold design variables and applications / Biomaterials, 2003, V. 24, N. 24, pp. 4,337-4,351; Shtilman M.I. et al. Epoxy-containing porous hydrogels of poly- (2-hydroxyethylmethacrylate): study of the influence of synthesis conditions / Plastics, 2002, No. 7, p. 24-28; Lozinsky V.I. Cryogels based on natural and synthetic polymers: production, properties and applications / Uspekhi Khimii, 2002, V. 71, No. 6, p. 559-585].

One of the most common methods for the synthesis of macroporous hydrogels is to obtain cryogels, for example, based on polyvinyl alcohol (PVA), formed upon freezing and subsequent thawing of solutions of this polymer [patent RU 2070901 C1, publ. 12/27/1996].

However, as a rule, such systems are thermally unstable and break down, passing into an aqueous solution when heated, and require fixing the structure using additional, often toxic, crosslinking reagents or hard radiation. All this greatly complicates and increases the cost of technology for their production, and also significantly limits the possible scope.

To obtain macroporous PVA-based hydrogels devoid of these drawbacks, we synthesized a modified PVA-based polymer containing unsaturated bonds in the side chain in an amount sufficient to form a three-dimensional spatial structure in the presence of radical polymerization initiators, with a slight change in physicochemical and toxicological properties modified polymer compared to the original polyvinyl alcohol [Artyukhov A.A. Macroporous hydrogels based on crosslinked polyvinyl alcohol / Abstract of dissertation for the degree of candidate of chemical sciences. - Moscow, 2006. - 18 p.].

A known method of obtaining a porous PVA hydrogel through the use of crosslinking agents with high toxicity, which must be carefully removed from the finished gel, or by radiation [Golunova A.S. et al. Porous polymer hydrogels based on polyvinyl alcohol and its derivatives containing charged groups / Advances in Chemistry and Chemical Technology, 2010, T. XXIV, No. 4 (109), p. 23-32].

All this requires additional purification of products, significantly limits the scope of their application, and also complicates the production technology.

Together with PVA, biodegradable polymers are often used - chitosan, collagen. And in this case, cryotropic gelation technology is used, freeze-drying during the day under vacuum [Monograph "Chitosan" / ed. Scriabin K.G., Mikhailova S.N., Varlamova V.P. - M .: Center "Bioengineering" RAS, 2013. - 593 p .; Podorozhko E.A. et al. Study of cryostructuring of polymer systems. Complex and composite polyvinyl alcohol cryogels containing, respectively, soluble and insoluble forms of chitosan / Colloid Journal, 2016, T. 78, No. 1, p. 75].

There is also a method of obtaining a porous sorption dressing material based on PVA, a crosslinking agent, a mineral acid, sodium chloride, a foaming agent [patent RU 2151615 C1, publ. 06/27/2000]. The quantitative ratio of PVA to crosslinking agent is 100-170 parts of crosslinking agent per 100 parts of PVA.

The disadvantage of this material is the lack of thermal stability of the product, the relatively small number of pores and their total volume. It is essential that the product must be thoroughly cleaned of the crosslinkable agent. These methods are multi-stage and long-lasting.

The synthesis of porous hydrogels is also possible during the polymerization of monomers in aqueous frozen solutions of water-soluble unsaturated derivatives of PVA. The unsaturated radical introduced into the side chain contains one or two unsaturated groups and provides the formation of a spatial structure under conditions of radical polymerization and copolymerization. A radical may contain an unsaturated acid residue, for example, acrylic, methacrylic, sorbic, crotonic, cinnamon, or an alkene group, and the unsaturated group may also be introduced as a side acetal substituent. The material has increased thermal stability, developed porosity and high drainage ability. Polymeric hydrogels for medical purposes are obtained in the presence of biologically active compounds and are used to create coatings in the treatment of wounds and burns, macroporous hydrogel polymeric materials and products based on them are used as implants, substrates for cell engineering, matrices with controlled release of drugs, drainage agents, and etc. [patent RU 2328313 C2, publ. 07/10/2008; Patent RU 2612703 C1, publ. 03/13/2017; patent RU 2198686 C2, publ. 02/20/2003].

However, these methods are replete with the presence of a large number of stages, organic substances and require additional purification and the duration of operations.

Also described is the synthesis of polymethylsiloxanes (hydrogels of methylsilicic acid), which can be used as adsorbents in various fields of technology, in particular in medicine, as enterosorbents for excretion of medium molecular organic toxic metabolites. These compounds are synthesized due to the need to obtain sorbents with increased sorption capacity and selectivity for medium molecular metabolites [patent RU 2111979 C1, publ. May 27, 1998].

In the work [Pashkin I.I. et al. Structuring in polyvinyl alcohol-glycol-water systems / Plastics, 2011, No. 2, p. 11-15] the effect of glycols of various nature and concentration introduced into the reaction system on the properties of PVA-based form-stable hydrogels obtained by freezing mixtures was studied. In contrast to the structure of PVA-water cryogels, gels from ternary systems have a relatively regular finely porous structure consisting of globular formations, while the pore size is 60-80 nm, which is an order of magnitude larger than the average pore size of PVA-water cryogels. The obtained durable application materials have found application in medicine and cosmetology.

Thus, the considered methods for the synthesis of porous hydrogels use mainly the cryogenic technology of aqueous solutions of polymers (PVA) or the synthesis of polymers with appropriate additives (for example, cross-linking agents) with subsequent operations, including cryogenic drying, purification, which complicates the multi-stage technology and increases synthesis time. It should be emphasized that in these methods, only in the samples dried by cryogenic drying are the pores formed. In the swollen state, the pores are filled with solvent (water).

In the present invention, the method for producing a porous form-stable hydrogel is based on the sol-gel technology and uses microwave radiation (MVI) as an effect on the reaction system.

The main advantage of the sol-gel method is the high degree of homogenization of the starting components. This is achieved by dissolving the salts and oxides of the starting materials in the starting solution. The sol-gel method, in comparison with the traditional scheme of synthesis of substances, has a simplified technological scheme of synthesis. This method allows to reduce energy consumption and a high degree of purity of products at all stages of synthesis with a minimum of costs for its achievement. It becomes possible to obtain products using this method that are characterized by: a monophasic crystalline structure with a high degree of perfection; strictly stoichiometric composition; lack of extraneous phases. An extremely important role in the sol-gel process is played by the processes of solvent removal from the gel (drying). Depending on the method of their implementation, various synthesis products (xerogels, ambigels, cryogels, aerogels) can be obtained. Common features of these products are the preservation of nanoscale structural elements and fairly high values of the specific surface [Eliseev A.A., Lukashin A.V. Functional nanomaterials. - M .: FIZMATLIT, 2010 .-- 456 p .; Maksimov A.I., Moshnikov V.A., Tairov Yu.M., Shilova O.A. The basics of sol-gel technology of nanocomposites. - SPb .: Technomedia LLC, 2007. - 255 p .; Shabanova N.A., Sarkisov P.D. The basics of sol-gel technology of nanosized silica. - M.: IKC "Akademkniga", 2004. - 208 p .; Cheong K.Y. et al. Electrical and optical studies of ZnO: Ga thin films fabricated via the sol-gel technique / Thin Solid Films, 2002, V. 410, pp. 142-146; Li Y. et al. Effect of aging time of ZnO sol on the structural and optical properties of ZnO thin films prepared by sol-gel method / Applied Surface Science, 2010, V. 256., pp. 4543-4547).

In the case of using microwave radiation, the synthesis of the hydrogel can be carried out simultaneously with the formation of a porous structure. Microwave radiation to produce pores can also be used on finished hydrogels.

Microwave radiation (MVI) refers to an environmentally friendly type of technology, "green chemistry" and is one of the promising methods that can reduce energy consumption and increase the rate of formation of end products [Kubrakova I.V. Microwave Radiation in Analytical Chemistry: Possibilities and Prospects of Use / Uspekhi Khimii, 2002, V. 71, No. 4, p. 240-278; Romanova N.N. et al. Microwave irradiation in organic synthesis / Advances in Chemistry, 2005, T. 74, No. 11, p. 1059-1101; Kirsh Y.E. et al. Structural transformations and water associate interactions in poly-N-vinylcaprolactam-water system / European Polymer Journal, 1999, V. 35, N. 2, pp. 305-316; Whittaker A.G. et al. The application of microwave heating to chemical syntheses / Journal of microwave power and electromagnetic energy, 1994, V. 29, N. 4, pp. 195-219].

The present invention does not have the closest analogue, since the proposed method is based on a combination of two although well-known technological methods (sol-gel technology and microwave exposure), however, the joint use of these techniques to obtain porous hydrogels is not known.

The use of polar compounds in the synthesis of hydrogels of hydrogels provides a strong effect of microwaves on the system, heating and evaporation of individual components, which causes the formation of a porous structure. Depending on the nature of the compounds and their concentration, time and power of MVI, both the number of pores and their size can be varied. The use of MVI as a promoter in the preparation of porous hydrogels based on poly-N-vinylamides and tetraethoxysilane using the sol-gel technology has several advantages:

1. The selectivity of the impact of MVI on certain components of the reaction system. It is known that the ability of a material to convert electromagnetic energy into heat is characterized by the dielectric loss tangent: tanδ = ε ₁ / ε ₂ , where ε ₁ is the dielectric loss coefficient (the efficiency with which the electromagnetic field energy is converted into heat), ε ₂ is the dielectric constant [ Tselinsky I.V. et al. The use of microwave heating in organic synthesis / Journal of General Chemistry, 1996, T. 66, No. 10, p. 1699-1704]. The introduction of compounds with different values of the dielectric loss parameters allows you to vary their ability to heat (evaporation). Depending on the tanδ value, the solvents are divided into three groups: strong tanδ> 0.5, to which alcohols belong; average tanδ = 0.1-0.5 (for water tanδ = 0.123); weak tanδ <0.1 (for acetone tanδ = 0.054).

2. MVI ensures the inertia of the heating of the system and, unlike convection heating, penetrates quickly throughout the sample volume.

3. Given that the effects of MVI are hydrogels containing a certain amount of water, which, if possible, must be preserved in some cases, the speed and time of MVI are of decisive importance. In this regard, the solvents additionally introduced into the reaction system should have a larger dielectric loss tangent than water parameters, which determined the choice of solvents in the present invention.

4. The use of microwave heating must be coordinated with the energy balance of the gelation reaction, which is the sum of the hydrolysis of tetraethoxysilane (TPP) and polycondensation, which can occur both with absorption and heat generation. There is no unequivocal opinion on the balance in the literature: hydrolysis of thermal power plants is an exothermic process and the system can heat up to 50-60 ° С, polycondensation is endothermic, although the balance depends on the nature of the catalyst [Farus O.A. Investigation of the effect of the type of catalyst on the gelation processes of the sol-gel system based on tetraethoxysilane / Internet journal "SCIENCE", 2015, V. 7, No. 4, p. 1-10]. On the other hand, the rate of decrease in the concentration of TPPs in the reaction mass during hydrolysis increases with increasing temperature. All these data must be taken into account when using MVI heating in the synthesis of hydrogels: hydrolysis time and gelation time (polycondensation, viscosity increase). [Antoshkina E.G. et al. Obtaining composite gels based on tetraethoxysilane modified with inorganic substances / Electronic scientific and practical journal "Research in the field of natural sciences", 2014, No. 8; Shabanova N.A., Sarkisov P.D. Sol-gel technology. Nanodispersed silica. - M .: BINOM, 2012 .-- 328 p .; Skorodumova O.B. et al. Investigation of the gelation mechanism in silica hybrid gels with a reduced tendency to aggregation / Bichuk NTU “KhP1”, 2014, No. 60 (1102), p. 14-19; Whittaker A.G. et al. Application of microwave heating to chemical syntheses / Journal of microwave power and electromagnetic energy, 1994, V. 29, N. 4, pp. 195-219].

5. A particularly valuable property of macroporous hydrogels obtained by the proposed technology is the preservation of their porosity during repeated swelling and drying, which does not require additional operations to fix the structure. In addition, the evaporation of organic compounds under the influence of MVI minimizes their amount in the hydrogel, which reduces the number of stages of the process (purification of the hydrogel) and provides non-toxic composite hydrogels. The presence in the reaction mixture of an organic solvent and water suggests the formation of azeotropic mixtures, the composition of which is dominated by organic matter [Sventoslavsky V. Azeotropy and polyaseotropy. - M .: Chemistry, 1968 .-- 244 p .; Ogorodnikov S.K., Lesteva T.M., Kogan V.B. Azeotropic mixtures. Directory. - L .: Chemistry, 1971. - 648 p.], And microwave heating will also help to reduce their concentration in hydrogels, especially since the boiling point of azeotropic mixtures is usually lower than the boiling point of individual solvents.

The technical result of the present invention is to obtain porous form-resistant polymer hydrogels based on poly-N-vinylamides, as well as to preserve the porosity of these hydrogels during swelling and drying.

The specified technical result is achieved through the joint use of sol-gel technology and microwave exposure to obtain porous polymer hydrogels.

More specifically, in the first embodiment, the method of producing a porous form-stable polymer hydrogel is characterized in that the hydrogel is obtained by sol-gel technology in the presence of a reaction mixture consisting of poly-N-vinylamide, a precursor tetraethoxysilane (TPP), a main catalyst and 0.5 -4.0 rpm % organic solvent, followed by exposure to the specified reaction mixture of microwave radiation (MVI) until the organic solvent evaporates to form pores in the polymer hydrogel.

In the second embodiment, the method for producing a porous form-stable polymer hydrogel is characterized in that the non-porous polymer hydrogel obtained by the sol-gel technology in the presence of a reaction mixture consisting of poly-N-vinylamide, a precursor tetraethoxysilane (TES) and the main catalyst is swollen in an organic solvent, followed by the action of MVI on the swollen polymer hydrogel until the organic solvent evaporates to form pores in the polymer hydrogel.

As an organic solvent, solvents that actively interact with MVI can be used, which leads to their evaporation and the formation of pores in the hydrogel. These solvents are characterized by a dielectric loss tangent (tan δ) of greater than 0.5. Such an organic solvent is preferably selected from propanol, triethylene glycol, ethanol.

Non-polar volatile solvents, for example, hexane, can also be used as an organic solvent.

In some embodiments, a thickener may be added to the reaction mixture to reduce the ripening time of the hydrogel. As such a thickener, a dye was used - methyl orange.

The most preferred basic catalyst is triethanolamine. However, it is also possible to use other basic catalysts known from the prior art [see, for example: patent RU 2371451 C2, publ. 10/27/2009; patent RU 2472778 C2, publ. 01/20/2013].

The source of the electromagnetic field was Discover microwave ovens (CEM Corp., USA, 2.45 GHz frequency) and Samsung PG 83R (China, 2.45 GHz frequency). MVI power: 100-800 W, processing time 5-18 min.

In embodiments of the invention, poly-N-vinylcaprolactam (PVC) or poly-N-vinylpyrrolidone (PVP) with a molecular weight of 10 ⁶ Da was used as poly-N-vinylamides, and propanol-2, ethanol, triethylene glycol (organic solvents) were used ( TEG).

The concentrations of the main catalyst (triethanolamine) and the precursor (tetraethoxysilane) were selected in the ranges of 0.02-0.6 and 2.0-8.0 vol. % respectively. The amount of organic solvent was varied in the range of 0.5-4.0 vol. %

The maturation of the hydrogel was evaluated qualitatively by the transparency of the samples, as well as by the rate of increase in viscosity of the reaction mixture, the rate and maximum degree of swelling in water. The pore size of the hydrogel ranges from 20 to 700 microns.

In FIG. 1 shows the dependence of the degree of swelling of hydrogels on time: curve 1 - hydrogel according to example 1, curve 3 - hydrogel according to example 7.

In FIG. 3-6 are microphotographs of the synthesized porous form-stable hydrogels based on poly-N-vinylamides; for comparison, a microphotograph of a hydrogel without MVI processing is shown (Fig. 2). Photographs taken with Microscope Digital Comera Levenhuk C-Series Zoom Joy (China).

Example 1 (comparative example). 10 ml 5 vol. % aqueous solution of PVC was mixed with 0.07 vol. % of the main catalyst (triethanolamine) and with 5 vol. % precursor (TPP). The reaction mixture was stirred for 10 minutes and left at room temperature until the hydrogel matured (9 days). A dense, transparent pore-free hydrogel was obtained (FIG. 2).

Example 2 (comparative example). 10 ml 5 vol. % aqueous solution of PVP was mixed with 0.07 vol. % of the main catalyst (triethanolamine) and with 5 vol. % precursor (TPP). The reaction mixture was stirred for 10 minutes and left at room temperature until the hydrogel matured (10 days). A dense transparent pore-free hydrogel was obtained.

Example 3. The hydrogel obtained in example 2 was subjected to swelling in propanol, the degree of swelling of 18%. Next, the MVI swollen hydrogel was processed (power 800 W, processing time 5 min). The obtained porous hydrogel (Fig. 3).

Example 4. Porous hydrogel obtained by the method in accordance with example 3, with the exception that the power MVI was 100 watts, and the processing time is 18 minutes

Example 5. To the reaction mixture (described in example 1) was added an organic solvent (ethyl alcohol) in an amount of 0.5 vol. % After stirring, the mixture was subjected to MVI (power 100 W, processing time 10 min). The hydrogel ripening time is 13 days. The obtained porous hydrogel (Fig. 4).

Example 6. To the reaction mixture (described in example 1) was added an organic solvent (TEG) in an amount of 0.5 vol. % After stirring, the mixture was subjected to MVI (power 100 W, processing time 18 min). The hydrogel ripening time is 13 days. The obtained porous hydrogel (Fig. 5).

Example 7. The effect of MVI on the azeotropic mixture

The effect of MVI on the azeotropic mixture (AS) is shown by the example of the synthesis of a porous hydrogel in the presence of the reaction mixture described in Example 1, to which a volatile non-polar organic solvent hexane (1.0 vol.%) Was added. The composition of the azeotropic mixture: water / hexane = 6/94 (by volume), the boiling point of which is 100 ° and 69 ° C, respectively, and the boiling point of the AC is 62 ° C [Sventoslavsky V. Azeotropy and polyaseotropy. - M.: Chemistry, 1968 .-- 244 p. \ Ogorodnikov S.K., Lesteva T.M., Kogan V.B. Azeotropic mixtures. Directory. - L .: Chemistry, 1971. - 648 p.]. Although hexane itself does not interact with MVI, heating of the system promotes the rapid evaporation of hexane and AS with the formation of pores. The degree of swelling of the porous hydrogel (PVC) formed under these conditions in water reaches 8000–9000% (Fig. 6).

Thus, the above examples demonstrate the possibility of structural changes in hybrid organo-inorganic hydrogels based on poly-N-vinylamides and tetraethoxysilane synthesized by sol-gel technology using MVI to obtain a porous hydrogel. The proposed method allows you to save the porosity of the polymer hydrogel in a swollen and dry state. The use of a thickener - dye methyl orange, participating in complexation with poly-N-vinylamides, reduces the ripening time of the hydrogel by 1.5-2.0 times, which is an additional technical effect achieved in the implementation of a special case of the proposed methods. The pore size according to the proposed methods for the synthesis of porous polymer hydrogels ranges from 20-700 microns. The presence of pores increases the maximum degree of swelling by 1.6-3.5 times, the swelling rate of a porous hydrogel increases by 1.5-3.0 times compared with non-porous systems, which will allow the use of such hybrid organo-inorganic compositions for immobilization of drugs ( wound coverings), as effective sorption systems, etc.

Claims (7)

1. A method of obtaining a porous form-resistant polymer hydrogel, characterized in that the hydrogel is obtained by sol-gel technology in the presence of a reaction mixture consisting of poly-N-vinylamide, a precursor - tetraethoxysilane (TPP), a main catalyst and 0.5-4, 0 about % organic solvent, followed by exposure to the specified reaction mixture of microwave radiation (MVI) until the organic solvent evaporates to form pores in the polymer hydrogel, while the organic solvent is selected from a solvent with a dielectric loss tangent (tan δ) greater than 0.5 or non-polar volatile solvent. 2. A method of obtaining a porous form-stable polymer hydrogel, characterized in that the non-porous polymer hydrogel obtained by sol-gel technology in the presence of a reaction mixture consisting of poly-N-vinylamide, a precursor tetraethoxysilane (TPP) and a main catalyst is subjected to swelling in an organic solvent, followed by the action of MVI on the swollen polymer hydrogel until the organic solvent evaporates to form pores in the polymer hydrogel, while the organic solvent is selected from solvent with a tan δ value greater than 0.5; or from a non-polar volatile solvent. 3. The method according to any one of paragraphs. 1 or 2, characterized in that the poly-N-vinylamide is selected from poly-N-vinylcaprolactam and poly-N-vinylpyrrolidone. 4. The method according to any one of paragraphs. 1 or 2, characterized in that the solvent with a value of tan δ greater than 0.5 is selected from propanol, triethylene glycol, ethanol. 5. The method according to any one of paragraphs. 1 or 2, characterized in that the non-polar volatile solvent is hexane. 6. The method according to any one of paragraphs. 1 or 2, characterized in that triethanolamine is preferably used as the main catalyst. 7. The method according to any one of paragraphs. 1-6, characterized in that a thickener is added to the reaction mixture — a dye methyl orange.

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