D. M. Mognonov

pH-Sensitive hydrogels based on polyhexamethyleneguanidine hydrochloride

The possibility to prepare pH-sensitive hydrogels based on polyhexamethyleneguanidine hydrochloride was explored. The equilibrium swelling rate of the hydrogels obtained at different monomer ratios was examined in relation to pH of the medium.

Proton conductivity of new type medium-temperature proton exchange membranes

Among polymer fuel cells (FC), there is a class of devices where phosphoric acid is used as electrolyte. The retention of acid in a polymer matrix is provided by binding a part of its molecules with basic groups of the polymer. Operating temperature for such medium-temperature FC can attain 150 °C due to high thermal stability and relatively high proton conductivity at low humidity [1]. Increased operating temperature of such FC provides many advantages as compared with low-temperature FC with solid polymer membranes, among which increased tolerance of catalytic materials to CO poisoning is one of the most important parameters. Moreover, high temperature facilitates the organization of water management in the fuel cell: the water does not condense in the liquid phase, and there is no danger of flooding of electrode pores during operation. Thus, CO-enriched hydrogen produced by the reforming of natural gas, other hydrocarbon feedstocks, and alcohols can be used for their work [2, 3]. Nowadays, the most developed polymer electrolyte membranes for medium temperature FC are based on various condensation polymers, composite materials, polymers with nitrogen-containing heterocycles, and complexes of polymers with acids [4]. For mediumand high-temperature FC, the most studied proton conductive membranes are those based on polybenzimidazole (PBI) and its derivatives doped by phosphoric acid [5, 6]. Such membranes show high thermal stability and proton conductivity in the absence of water. However, the major drawback of these materials is associated with acid leaching [7]. Condensation of water vapor formed by the FC operation, for example, by stopping and cooling the battery, leads to phosphoric acid leaching from the electrolyte and its degradation, and penetration of acid on the structural elements leads to corrosion of the latter [8–10]. Thus, the search for new polymer materials that can safely hold the acid anion is one of the important tasks of developing mediumtemperature FC. This work reports on the analysis of physicochemical properties including proton conductivity of a new class of composite proton exchange membranes based on N-phenylsubstituted polyhexamethylene guanidine (PHMG) and poly-m-phenylene isophthalamide (phenylone) doped with phosphoric acid (PHMGP-PA) at different temperatures and environmental humidity. The presence of a strong ionic bond between protonated PHMGP and phosphoric acid anions allowed one to expect that the composite material is capable to retain phosphoric acid even in conditions of high humidity and temperature. * Alexander E. Ukshe ukshe@mail.ru

Improving the wear resistance of polytetrafluoroethylene friction surface

Results obtained in a study of doping of the friction surface of polytetrafluoroethylene with polymerpolymeric mixtures based on aromatic polyheteroarylenes with a structure of a semi-interpenetrating network are analyzed. It is shown that polymer-polymeric mixtures composed on polybenzimidazoles and poly(amino imide) resin are structurally active with respect to polytetrafluoroethylene and substantially improve the tribological and stress-strain properties of composite materials based on this compound.

New tribological composites based on polytetrafluoroethylene

Some research directions of formulations and technology of development for polymeric antifrictional composites (solid lubrican Fts) with increased physicomechanical tribological properties are considered. These composites are based on polytetrafluoroethylene and semi-interpenetrating polymer network (SIPN) matrices and mixed organic–inorganic fillers. Comparative analysis of qualification of materials when tested in field conditions and express testing using laboratory equipment provide a reliable screening of the service life of the materials to evaluate the performance of machines and mechanisms operating under the climatic conditions of the Russian North and the Arctic.

Polymeric hydrogels based on polyhexamethylene guanidine hydrochloride and formaldehyde

A new method for the synthesis of hydrogels based on polyhexamethylene guanidine hydrochloride was proposed. The use of formaldehyde as a cross linking agent for binding the terminal amino groups of the polymer chain to form a center branch thereon underlies the method.

Synthesis of Polyalkylguanidine Hydrochloride Copolymers and Their Antibacterial Activity Against Conditionally Pathogenic Microorganisms Bacillus Cereus and Escherichia Coli

Copolymers based on aliphatic diamines of various methylene chain lengths and guanidine hydrochloride were prepared by polycondensation in the melt. Antibacterial activity of water-soluble copolymers based on guanidine against conditionally pathogenic microorganisms Escherichia coli and Bacillus cereus was evaluated using diffusion in agar. Arelationship was found between the ratio of the number of hydrophobic methylene groups to the number of ionized guanidines and the antibacterial activity of the copolymers. Several samples showed high antimicrobial activity as compared with polyhexamethyleneguanidine hydrochloride (PHMGHC), which is widely used as a medical disinfectant.

Composite proton-conducting membranes based on poly(ethylene glycol vinyl glycidyl ether)

Composite proton-conducting membranes in the form of interpolymer films are prepared in an aqueous medium from sulfo-acid-modified poly(ethylene glycol vinyl glycidyl ether) and poly(vinyl alcohol). The initial poly(hydroxysulfo acid) is synthesized through the radical polymerization of ethylene glycol vinyl glycidyl ether followed by modification with sodium sulfite via epoxy groups and treatment with a cationite in the H form. The proton-conducting membranes feature improved thermal stability (200–250°C), a breaking strength of 1.0–8.9 MPa, elasticity (a relative elongation at break of 1.0–8.2%), chemical resistance, and specific proton conductivity attaining 10−1 S/cm after doping with orthophosphoric acid.

Preparation of polybenzimidazoles by oxidative dehydrocyclization of polyamidines

Dehydrocyclization of polyamidines into polybenzimidazoles under the action of various oxidants was studied. The strength and proton conductivity of membranes based on a blend of the polybenzimidazole obtained with poly(amino imide) resin were determined.

Synthesis of aromatic polyamidines in Eaton’s reagent

Aromatic polyamidines are prepared via the polycondensation of dicarboxamides and diamines in Eaton’s reagent. The polymers are investigated by elemental analysis and IR and NMR spectroscopy. Polyamidines are well soluble in concentrated sulfuric acid and concentrated formic acid and in polar organic solvents, and temperatures corresponding to their 10% weight losses are in the range 245–280°C.

Composition, Structure, and Properties of a Composite Material Based on Polytetrafluoroethylene and Oxyfluoride Glass–Ceramic

The morphology, structure, phase composition, and properties of composite materials based on polytetrafluoroethylene and oxyfluoride glass–ceramic of the composition 18LiF–31SiO2–19B2O3–24BaO–8TiO2 were studied.