E. N. Vlasova

Synthesis of multicentered polyimide initiators for the preparation of regular graft copolymers via controlled radical polymerization

Multicentered initiators for the controlled (pseudoliving) radical polymerization are synthesized via polymer analog transformation of hydroxyl-containing polyimides based on o-aminophenols. Conditions providing variations in the degree of functionalization of polyimides by initiating 2-bromoisobutyrate groups are determined, and optimum conditions for the preparation of macroinitators containing the above groups in each repeat polyimide unit are found. Via the method of controlled radical polymerization with the atom transfer on multicentered macroinitiators in the presence of complexes of univalent copper halides, graft copolymers of poly(methylmethacrylate) on polyimide backbone are obtained. Molecular-mass characteristics of graft copolymers are studied via multiple-detection size-exclusion liquid chromatography. Preparation of graft copolymers (polymer brushes) with a homogeneous grafting density and a homogeneous length of side chains necessitates grafting of the side chain on the polyimide initiator, which contains initiating groups in each repeat unit.

Optical constants of industrial polymers in the IR region

The optical constants have been measured by the techniques of IR transmission and ATR spectroscopy in the range 4000–400 cm−1 for four industrial polymers: polymethyl methacrylate, polystyrene, polyethylene, and polytetrafluorethylene.

Specific features of cellulose and chitin dissolution in ionic liquids of varied structure and the structural organization of regenerated polysaccharides

Solubility of cellulose, chitin, and chitosan in seven ionic liquids of varied structure was studied. It was found that pressure, temperature, and amount of an aprotic diluent (dimethyl sulfoxide) affect the dissolution of cellulose and chitin in an ionic liquid. The variation of the degree of polymerization of cellulose and chitin in ionic liquid solutions was studied. IR Fourier spectroscopy and X-ray diffraction analysis were used to examine the structural organization of hydrated cellulose and chitin films obtained.

Grafting copolymerization of vinyl monomers on polyimide macroinitiators by the method of atom transfer radical polymerization

Graft copolymers with the main polyimide chain and side chains of poly(n-butyl acrylate), poly(tert-butyl acrylate), poly(methyl methacrylate), poly(tert-butyl methacrylate), polystyrene, and polystyrene-block-poly(methyl methacrylate) were synthesized by atom transfer radical polymerization on the multicenter polyimide macroinitiators in the presence of the halide complexes of univalent copper with nitrogen-containing ligands. Polymerization of metha-crylates is most efficiently developed on the polyimide macroinitiators. The obtained graft copolymers initiate the secondary polymerization (“post-polymerization”) of methyl methacrylate. The conditions of detachment of side chains of graft polymethacrylates that do not involve the ester groups of their monomeric units were found. The molecular mass characteristics of the graft copolymers and isolated polymers, being the detached side chains of the copolymers, were determined. The detached side chains of different chemical structures have low values of the polydispersity index. The procedure developed was used for the preparation of new graft polyimides with side chains of poly-4-nitro-4′-[N-methylacryloyloxyethyl-N′-ethyl]amino-azobenzene that cause the nonlinear optical properties and with the side chains of poly(N,N-dimethylaminoethyl methacrylate) that cause the thermosensitive properties of the copolymers.

Immobilization of proteolytic enzymes trypsin and α-chymotrypsin to cellulose matrix

Trypsin and α-chymotrypsin were immobilized on a microcrystalline cellulose matrix by adsorption interaction with cellulose. The adsorption of enzymes was determined as a function of their concentration and the pH of solutions. Mechanisms of enzyme binding to functional groups of cellulose were suggested.

Characteristics of composite films based on methyl cellulose and poly(N-vinylformamide) prepared from solutions in water and dimethyl sulfoxide

The stress-strain characteristics of composite films based on methyl cellulose and poly(vinylformamide) prepared from solutions of polymer blends in water and dimethyl sulfoxide are studied. The temperature of relaxation transitions in the mixed films and the concentration interval where the polymers are compatible are defined via the thermomechanical method and dynamic mechanical analysis. The effect of the nature of a solvent on the mechanism of crystallization of methyl cellulose, the stress—strain characteristics of the composite films, and the compatibility between the polymers is investigated.

Compatibility of carboxymethyl cellulose ionized to various degrees with poly-N-vinylformamide in composite films

Composite films were obtained from aqueous solutions of blends of carboxymethyl cellulose ionized to various degrees and poly-N-vinylformamide. The composition ranges in which the polymers are compatible were determined by solvent vapor sorption and by dynamic mechanical analysis. The heat resistance of the films and the interaction of the polymers in the solid state were examined by DSC, TGA, and Fourier IR spectroscopy.

Distribution of zirconia nanoparticles in the matrix of poly(4,4′-oxydiphenylenepyromellitimide)

Poly(4,4′-oxydiphenylenepyromellitimide) is used as a polymer matrix for incorporation of zirconia nanoparticles with different compositions (ZrO2 and Y0.03Zr0.97O1.985), sizes (20 ± 5 and 10 ± 2 nm), and morphologies (spheres, hollow spheres, rods). The nanoparticles are incorporated during the synthesis of poly(amido acid), a prepolymer of polyimide, and ZrO2 nanoparticles are pretreated with organosilicon compounds (tetraethoxysilane, γ-aminopropyltriethoxysilane, and 3-(trimethoxysilyl)propyl methacrylate). The effect of surface modification of ZrO2 nanoparticles on their distribution in poly(4,4′-oxydiphenylenepyromellitimide), depending on the type of the organosilicon compound as well as on the dispersity, shape, and chemical composition of particles, is studied.

Chemical and structural transformations in chitosan films in the course of storage

Changes in the functional composition of chitosan films in the course of storage under ambient conditions were examined by conductometric titration and IR spectroscopy. The deformation-strength and thermal properties of the films were studied, and their supramolecular structure was analyzed by X-ray diffraction.

Molecular mobility of chitosan and its interaction with montmorillonite in composite films: Dielectric spectroscopy and FTIR studies

The interaction of chitosan in the basic form with montmorillonite at different concentrations in composite films is studied with the use of dielectric spectroscopy and FTIR measurements. It is shown that the interaction of amino groups and primary hydroxyl groups of chitosan with local charges on the surfaces of montmorillonite nanoparticles is responsible for a change in the system of intramolecular and intermolecular hydrogen bonds that is typical for polysaccharides. The glass-transition temperature of chitosan in the composite systems is measured.