S. S. Ivanchev

Fluorinated proton-conduction nafion-type membranes, the past and the future

Most of key decisions concerning the energetic safety problems, aimed to minimize climatic changes upon an increase in the energy consumption, diminish toxic discharges into the living environment, and save energy resources were formulated in the cooperation agreement between the European Community and the United States, signed on June 25, 2003, in Washington by the EC President R. Prodi, Greek Prime Minister K. Simitis, and United States President J. Bush [4]. The energy policy of the countries that signed the agreement was based on hydrogen energetics and use of fuel cells as the most optimal variants of implementation of stable energy supply systems.

Composite polymer hydrogels

Methods of preparing and properties of composite hydrogels based on various hydrophilic polymers and their mixtures with inorganic nanosized additives are considered. The effect of the type of physical or covalent bonding between components on the formation of composite hydrogels and their characteristics is discussed. The biphasic character of composite hydrogels determines as a rule their advantages as supersorbents, membrane materials, living-tissue substitutes, drug carriers, and soft-contact-lens materials.

Design of schiff base-like postmetallocene catalytic systems for polymerization of olefins: IV. Synthesis of 2-(aryliminomethyl)-pyrrole and 7-(aryliminomethyl)indole derivatives containing cycloalkyl substituents

Reactions of 4,6-substituted 2-cycloalkylanilines with 1H-pyrrole-2-carbaldehyde and 1H-indole-7-carbaldehyde in methanol in the presence of formic acid gave the corresponding Schiff bases which can be used as ligands for titanium and zirconium complexes.

Design of postmetallocene catalytic systems of arylimine type for olefin polymerization: XIV. Synthesis of (N-Allyloxyaryl)salicylaldimine ligands and their complexes with titanium(IV) dichloride

By reaction of salicylaldehydes with bulky substituents in the positions 3 and 5 with o-, m-, and p-allyloxyaniline hydrochlorides in the presence of triethylamine a series of the corresponding (N-aryl)-salicylaldimines was obtained, which with TiCl2(OPr-i)2 afforded complexes of titanium(IV) dichloride L2TiCl2.

Effect of preparation conditions on nanostructural features of the NAFION® type perfluorinated proton conducting membranes

Features of the fine structure of three samples of perfluorinated Nafion® type membranes—Nafion-115, its Russian analogue MF-4SK, and a new similar material PFM-E produced according to our novel water-emulsion technique—have been characterized using the small-angle neutron scattering technique. A difference in the regularity of common elements of fine structure (cylindrical channels) in the membranes has been revealed. Nafion-115 has the most regular structure with a diffraction peak corresponding to the double channel diameter and an additional broad maximum in the scattering curve indicating a long-range order in the arrangement of straight cylindrical channels. For MF-4SK, in addition, twisted and less ordered channels have been observed. In the PFM-E sample channels have a tortuous and branched structure with diameters similar to Nafion-115. Only a short-range order (40–50 Å) in the arrangement of the channels has been detected, and correlation in their mutual orientation at longer distances is weakened. It has been supposed that the observed branched structure of the channels promotes an increase in water content and an improvement in proton conductivity.

Scientific principles of a new process for manufacturing perfluorinated polymer electrolytes for fuel cells

A new process for manufacturing a perfluorinated polymer electrolyte for proton-conducting membranes of fuel cells is presented. The process is based on the aqueous emulsion copolymerization of tetrafluoroethylene (TFE) with perfluoro(3,6-dioxa-4-methyl-7-octene)sulfonyl fluoride (FS-141) and characterized by a high productivity, reduced consumption of the expensive sulfonated monomer, and the possibility of controlling the equivalent weight (EW) of the resulting copolymer. The copolymers are characterized by a uniform composition in combination with optimal EW values and afford the synthesis of proton conducting membranes for fuel cells with properties comparable with those of commercial Nafion membranes. A mechanism of the copolymerization of TFE with FS-141 in an aqueous emulsion is proposed and confirmed by kinetic and topochemical data.

Polymer hydrogels with the memory effect for immobilization of drugs

Hydrogels with the memory effect are synthesized from crosslinked copolymers of 2-hydroxyethyl methacrylate and functional monomers (acrylic acid or dimethylaminoethyl methacrylate) via the method of template synthesis with the use of the drug cephazoline as a matrix. It is shown that the hydrogels show an increased sorption activity against the target drug and a slow rate of drug release from the hydrogel (the memory effect) under certain conditions. In combination with cephazoline, these hydrogels may be regarded as a new prolonged-drug-release system for the treatment of infectious diseases.

Bioligand carriers based on methyl methacrylate copolymers with N-vinylformamide or glycidyl methacrylate

Emulsifier-free emulsion copolymerization of methyl methacrylate with N-vinylformamide and glycidyl methacrylate initiated by a cationic or anionic azoinitiator in the presence of dextran is used to produce monodisperse polymer particles with a developed multifunctional surface. As a result, monodisperse particles are obtained with a diameter of 350–660 nm, the surface layer of which contains, in addition to carboxyl groups, amino or epoxy groups. The conditions are determined for the formation of multifunctional hydrophilic particle surface via the hydrolysis of comonomer units and residual groups of initiators. The limiting values of bovine serum albumin chemisorption (2.4 and 1.0 mg/m2 on the particles of methyl methacrylate copolymers with glycidyl methacrylate or N-vinyl formamide, respectively) indicate that the obtained particles have sufficient sorption capacity to be applied as carriers for immunoreagents.

Ethylene polymerization on titanium phenoxyimine complexes with different structures

The kinetics of ethylene polymerization in the presence of catalytic systems based on methylaluminoxane-activated titanium bis(phenoxyimine) complexes with different structures has been investigated in the temperature range 30–70°C. The structures of the complexes have different substituents at the imine nitrogen atom and in the phenoxy group in the ligand, which affect the activity of the system and the molecular weight of polyethylene resulting from polymerization over at least 1 h. The polymerization kinetics is most sensitive to the structure of the substituent at the imine nitrogen atom and to bulky substituents in the ortho position of the phenoxy group. The results obtained are explained. An attempt is made to classify the influence of the substituents in the ligands. Process conditions ensuring living polymerization have been found. The physicochemical properties and structural features of the polyethylenes obtained have been determined.

Water-Resistant Films and Coatings Based on Cross-Linking Styrene-Acrylate Latex Copolymers

Water-resistant films and coatings were prepared from latexes of copolymers of styrene, n-butyl acrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, and methacrylic acid. The degree of cross-linking of the copolymers in the course of film formation and the water resistance of the films and coatings, associated with this parameter and evaluated by the water absorption and mechanical properties of wet films, were studied in relation to the gross composition of the latex copolymer, conditions of its synthesis, distribution of functional groups responsible for cross-linking in a latex particle, and temperature of film formation.