Membrany i membrannye tehnologii

A comprehensive study of hemocompatibility and gas permeability of 1,2-disubstituted polyacetylenes: poly(1-trimethylsilyl-1-propyne) and poly(4-methyl-2-pentyne) was carried out. The polymers were synthesized based on 1-trimethylsilyl-1-propyne and 4-methyl-2-pentynemonomers on the catalytic systems NbCl₅ and NbCl₅/n-Bu₄Sn with formation of homopolymers containing 50 and 55% cis-units, respectively. The comparison of the obtained polyacetylenes and the thermoplastic polyolefin, poly(4-methyl-1-pentene), that currently is widely used as a thin-film coating of hollow fiber membranes for extracorporeal membrane oxygenation of blood (ECMO), was performed. The investigated polymers are highly hemocompatible as shown by morphofunctional status of blood cells analysis and tissue donors mesenchymal multipotent stromal bone marrow cells culture. In terms of hemocompatibility, poly(4-methyl-2-pentyne) was superior to poly(1-trimethylsilyl-1-propyne) and was comparable to poly(4-methyl-1-pentene). The studied polyacetylenes were shown to be significantly more permeable on oxygen and carbon dioxide than poly(4-methyl-1-pentene): poly(1-trimethylsilyl- 1-propyne) is permeablein 320 and 400 times, poly(4-methyl-2-pentyne) is in 60 and 90 times, respectively. Such parameters can significantly reduce the contact area of membranes with blood and reduce the size of oxygenators. Since poly(4-methyl-2-pentyne) has the high gas permeability in combination with the hemocompatibility comparable to poly(4-methyl-1-pentene), this polymer can be recommended as a promising material of a selective membrane layer for ECMO technology.

In this work cross-linked polymer membranes were obtained by heat treatment of films prepared from a solution containing a mixture of brominated poly(1-trimethylsilyl-1-propyne) [PTMSP] and polyfunctional amine polyethylenimine [PEI] as a cross-linking agent. The cross-linked products were identified on the basis of IR spectra, elemental analysis data, and the stability of the reaction products to the solvent (CCl₄) in which the original brominated PTMSP is soluble. According to the IR spectra, the crosslinking reaction occurs via the reactive C-Br bond in bromine-containing PTMSP with the participation of PEI amino groups at temperatures above 90°C. Cross-linking of bromine-containing PTMSP makes it resistant to organic solvents. An increase of PEI-content in the mixture correlates with an increase in the proportion of bromine atoms that have reacted. The cross-linked polymer transport parameters were studied for individual gases and in a methane/n-butane mixture (98.4 mol.% methane and 1.6 mol.% n-butane). In the series PTMSP – brominated PTMSP-Br – PTMSP-Br/PEI (before cross-linking) – PTMSP-Br/PEI (after cross-linking) the permeability to individual gases decreases. Cross-linked PTMSP in a methane/n-butane mixture demonstrates high permeability coefficients of n-butane (P _n-C4H10 = 12000 Barrer) and selectivity for the release of n-butane from a mixture with methane (α _n-C4H10/CH4 = 13).

For the first time, for the problem of high-performance ultrafiltration flat-sheet membranes casting, polyphenylene sulfones (PPSF) with chlorine and hydroxyl terminal groups were synthesized and studied. The synthesis of PPSF was carried out in dimethylacetamide at different ratios of 4,4′-dihydroxydiphenyl and 4,4-dichlorodiphenylsulfone monomers. Two samples with a predominant content of hydroxyl and chlorine terminal groups, PPSF-OH and PPSF-Cl, were studied using NMR, GPC and DSC methods. The coagulation values of polymer solutions in N-methyl-2-pyrrolidone (NMP), the mechanical properties and hydrophilicity of the materials were also determined. Both PPSF samples have high strength modulus (16.0–16.6 MPa). Using the method of deposition in water of PPSF solutions in NMP with PEG-400 additives, flat-sheet porous asymmetric m embranes with a mesoporous (diameter of about 7 nm) thin outer layer and finger-like macropores in the substrate were obtained. An increase in the proportion of –OH terminal groups increases the hydrophilicity of the polymer. This, in turn, made it possible to obtain flat-sheet membranes based on PPSF-OH with a water permeability of 66.1 l/m² h bar, which is 1.5 times higher than the water permeability of the PFSF-Cl membrane. At the same time, both membranes demonstrate the Blue Dextran (M_w = 70,000 g mol^–1) rejection of 99.9%.

The structural and transport (conductivity and diffusion permeability) properties of cation- and anion-exchange membranes with different dispersity of ion-exchange resin particles have been studied. Experimental cation-exchange MK-40 and anion-exchange MA-41 membranes with varying particle sizes of ion exchange resin from <20 μm to <71 μm are manufactured at LLC IE Shchekinoazot (Russia). A comparative analysis of the structural characteristics of membranes using SEM reveals the anisotropy in the properties of the surface and section. The internal phase of the membrane is characterized by large values of the fraction and size of the ion exchanger and macroporosity. A comparison of the concentration dependences of the specific conductivity and diffusion permeability of experimental membranes is performed. Analysis of the values of model transport and structural parameters shows that with a decrease in the size of ion exchanger particles, an increase in the conductivity of the gel phase is observed from 0.39 to 0.47 S/m and from 0.15 to 0.26 S/m for cation- and anion-exchange membranes, as well as a redistribution of current transfer paths in the membrane. An increase in the contribution of transfer through the channel of the internal equilibrium solution is revealed, while the transfer numbers of counterions changes slightly. Information about changes in the structure of transport channels in membranes with different sizes of ion exchanger particles, obtained based on the analysis of model parameters, is consistent with the data of independent studies of the morphology of their surface and section using the SEM method.