I. I. Gavrilova

Conformational Parameters of Poly(N-methyl-N-vinylacetamide) Molecules Through the Hydrodynamic Characteristics Studies

Water-soluble PMVA was synthesized by radical polymerization methods. A number of polymer samples were fractionated in the chloroform-diethyl ether system. Fractions were studied by molecular hydrodynamics methods (sedimentation velocity, translational isothermal diffusion and viscosity) in H(2)O and DMF. The molecular masses of fractions were determined and the Kuhn-Mark-Houwink-Sakurada relationships were obtained in the molecular mass range of 3.5 < M x 10(-3) g x mol(-1) <540. A negative temperature coefficient of the characteristic viscosity was obtained in both solvents. The Kuhn statistic segment length and the hydrodynamic diameter of the molecule were estimated for PMVA. The hydrodynamic volumes, occupied by the molecules of PMVA, poly(1-vinyl-2-pyrrolidone), poly(vinylformamide), and pullulan were compared.

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.

Conformations of sodium poly(styrene-4-sulfonate) macromolecules in solutions with different ionic strengths

Translational friction and viscosity of dilute solutions of sodium poly(styrene-4-sulfonate) with molecular masses of M = (5 × 104)−(85 × 104) are studied at different concentrations of low-molecular-mass salts. Molecular masses of the polymer are determined from the sedimentation-diffusion data. The study of the correlation between molecular masses and hydrodynamic characteristics resulted in ascertainment of the Kuhn-Mark-Houwink-Sakurada relationships for salt-free aqueous solutions of the polymer and solutions of the polymer in 0.2 M NaCl, 4.17 M NaCl, and 1.0 M KCl. It is shown that, as the ionic strengths of solutions are varied from minimum (H2O) to maximum (4.17 M), macromolecules of the strong polyelectrolyte sodium poly(styrene-4-sulfonate) change their conformations from rigid rods to coils and, then, approach a globular conformation. In terms of the Gray-Bloomfield-Hearst and Yamakawa-Fujii theories and within the framework of the weakly bent cylinder model, the statistical Kuhn segment length and the hydrodynamic diameter of sodium poly(styrene sulfonate) chains are estimated in 0.2 and 4.17 M NaCl, 1.0 M KCl, and salt-free aqueous solutions. The electrostatic component of the equilibrium rigidity is taken into account within the framework of the Odijk-Fixman-Skolnick and Dobrynin theories.

Properties of aqueous solutions of hydroxyethyl cellulose-poly(N-vinylformamide) blends and of the related composite films

The rheological properties of dilute and moderately concentrated aqueous solutions of hydroxyethyl cellulose-poly(N-vinylformamide) blends are studied. The stress-strain characteristics of the composite films are estimated. Dynamic mechanical analysis, the thermomechanical method, and the method of solvent-vapor sorption are used to determine the composition ranges of polymer compatibility and the temperatures of relaxation transitions in composite films. The structural organization of composite films is studied via X-ray diffraction analysis. The incorporation of one polymer into the matrix of another polymer entails changes in crystallization of the polymer dominating in the composite with respect to weight and causes an increase in the imperfectness of the crystal structure.

Solution behavior of methyl cellulose mixtures with poly(N-vinylformamide) in water and dimethyl sulfoxide

The rheological properties of diluted and moderately concentrated solutions of methyl cellulose mixtures with poly(N-vinylformamide) in water and dimethyl sulfoxide are investigated. Negative deviations of the viscosities of these solutions from the additive values are observed and explained by different mechanisms of solvation of macromolecules with water and dimethyl sulfoxide. Incompatibility of the polymers in a common solvent is discovered. This circumstance leads to the formation of a new system of hydrogen bonds and rearrangement of the structural organization of solutions.

Homopolymerization of N-vinylamides in the presence of water-soluble initiators and preparation of polyelectrolytes from the polymerization products

Homopolymerization of vinylformamide and N-methyl-N-vinylacetamide in water in the presence of 2,2′-azobis(2-methylpropanediamine) dihydrochloride and of the hydrogen peroxide-ammonium hydroxide system was examined. Hydrolysis of polyvinylformamide, poly-N-methyl-N-vinylacetamide, and poly-N-vinylacetamide with hydrochloric acid at 100°C was studied.

Dimensions and conformations of macromolecules of N-methyl-N-vinylacetamide and N-methyl-N-vinylamine hydrochloride in solutions in a wide interval of ionic strength

Fractions of the copolymer of N-methyl-N-vinylacetamide and N-methyl-N-vinylamine hydrochloride containing 15.7 ± 0.5% of charged units are obtained by radical polymerization, fractionation, and hydrolysis. Viscous flow, velocity sedimentation, and translational diffusion of their dilute solutions are studied in 0.2 M NaCl. Viscosimetric studies are also carried out in a wide range of ionic forces: from the minimum (~10–6 mol/L) to the maximum (6 mol/L). The hydrodynamic volumes and equilibrium rigidity of the copolymer under study are compared with the data obtained earlier for an uncharged homopolymer and a copolymer with a higher linear charge density (~44% of charged units) in solutions with different ionic strength. The correspondence of the values obtained to the theories of Odijk, Skolnik, and Fixman (OSF) as well as Dobrynin is discussed.

Properties of solutions of methyl cellulose blends with poly( N -methyl- N -vinylacetamide) in water and dimethylacetamide and of the related composite films

The rheological properties of dilute and moderately concentrated solutions of methyl cellulose blends with poly(N-methyl-N-vinylacetamide) in water and dimethylacetamide are studied, and the stressstrain characteristics of the composite films based on these blends are estimated. DSC, X-ray diffraction, and thermomechanical analysis are used to investigate the structural organization of composite films, to estimate the temperatures of relaxation transitions, and to determine the composition ranges in which the polymers are compatible and form mixed structures.

Sizes and conformations of hydrophilic and hydrophobic polyelectrolytes in solutions of various ionic strengths

The hydrodynamic characteristics of macromolecules of a random copolymer of N-methyl-N-vinylacetamide and N-methyl-N-vinylamine hydrochloride containing 43.6% charged units in the molecular-mass range of 27 × 103 to 355 × 103 are studied. For solutions in 0.2 M NaCl, sedimentation and translational-diffusion coefficients are determined. For salt-free solutions and for solutions in 0.2 and 5.0 M NaCl, the intrinsic viscosities of the fractions are found. The lengths of the statistical segments of the chains are estimated in terms of the Gray-Bloomfield-Hearst theory. The behavior of the polycation, whose uncharged counterpart is a hydrophilic polymer, is compared to the behavior of poly(sodium 4-styrenesulfonate), whose uncharged counterpart is a hydrophobic polymer. The comparison is based on normalized scaling relations. It is shown that the level of compaction of macromolecules of strong polyelectrolytes at a high ionic strength is determined by the degree of hydrophobicity of their polymer chains. Polyelectrolytes based on hydrophilic polymers cannot be compacted into a preglobular state; their chains preserve a swollen coil conformation up to maximally high values of ionic strength.