Stanislav I. Klenin

Poly(vinyl pyrrolidone)—C70 complexes in aqueous solutions

Abstract Aqueous solutions of poly(vinyl pyrrolidone)–fullerene complexes (PVP–C70) have been studied using static and dynamic light scattering methods. Two diffusive processes were detected. The slow diffusion was interpreted as dynamics of large intermolecular PVP–C70 complexes while the fast diffusion was associated with the presence of individual PVP molecules in solution. It was also shown that the molecular weights and dimensions of PVP–C70 complexes are smaller than for PVP–C60 by a factor of 2.5–3. In aqueous solutions of PVP–C70 complex the depolarization and dissymmetry of scattered light were observed in contrast to PVP–C60 solutions. It reveals the existence of anisotropic structures in PVP–C70 solutions. Intermolecular interactions within PVP–C70 complexes are weak and a hydrodynamic field can destroy complexes.

Conformational changes of a polyelectrolyte in mixtures of water and acetone

Samples of a polyelectrolyte poly(methacryloylethyl trimethylammonium methylsulfate), PMETMMS, with molar masses M w = 22-25 x 10 6 were examined with viscosity, static light scattering, and conductivity measurements in a water-acetone solvent. Because acetone is a nonsolvent for this polymer the measurements were performed to determine the influence of the solvent composition, the polymer concentration, and the presence of added ions on the conformation of the polyelectrolyte in mixed solvents. The possible influence ofa hydrodynamic field on the polymer conformation was also studied. The viscosity of the polymer solutions as a function of polymer concentration, as well as of the solvent composition, was studied using a broad range of shear rates. When the mass fraction of acetone in the solvent, γ, is below 0.5, the solutions show a usual polyelectrolyte behavior. When γ ≥ 0.80, the polymer adopts a compact conformation. This is observed as a decrease of the radius of gyration, R g , second virial coefficient, A 2 , the viscosity, and also as a change in the conductivity of the solution. The change in the polymer conformation may be induced also by dilution. When 0.60 ≤ γ < 0.80, a gradual decrease in the polymer concentration leads to a sudden decrease of the reduced viscosity, which indicates a decrease in the particle size. The values of M w measured by static light scattering were constant in all experiments.

Collapse of poly(methacryloylethyl trimethylammonium methylsulfate) on addition of acetone into an aqueous solution

Abstract The effect of the solvent composition on the conformation of a super high molar mass polyelectrolyte, M w =22–25×10 6 , dissolved in a water–acetone mixture was investigated using static and dynamic light scattering. When increasing the concentration of acetone above 80 mass percent, a reversible conformational change of macromolecules occurs, which causes a sharp decrease in the viscosity, a rise in the light scattering intensity, and also a decrease in the radius of gyration, R g , the hydrodynamic radius, R h , as well as in the second virial coefficient A 2 . The correlation function measured by dynamic light scattering changes from bimodal to unimodal indicating the formation of compact globular structures.

Electron microscopy studies on the coil‐to‐globule transition of a polyelectrolyte in a water–acetone mixture

A high molar mass polycation poly(methacryloylethyl trimethylammonium methylsulphate), PMETMMS, dissolved in mixtures of water and acetone, was studied using light scattering during the reversible coil-to-globule transition. When the mass fraction of acetone in the solvent mixture, γ, is higher than 0.80, PMETMMS adopts a globular state but does not aggregate. The collapse of PMETMMS can also be induced by the dilution of the polymer solution, if 0.70 ≤ γ < 0.80, and the solvent composition is kept constant. The results obtained by light scattering have been confirmed using a transmission electron microscope with which the collapse of PMETMMS has been observed. At high polymer concentration and 0.70 ≤ γ < 0.80, a transient network is formed: coils strongly interact with each other via dipole–dipole interactions in a thermodynamically poor solvent. At low concentration regime when 0.70 ≤ γ < 0.80, or in solutions with the mass fraction of acetone higher than 0.80, all the PMETMMS molecules are collapsed. In the intermediate region, the collapse of PMETMMS is gradual and coils, globules, as well as fragments of the network coexist in the solution.

Light Scattering Study of Aqueous Poly(Vinyl)pyrrolidone–Fullerene C70 Solutions

Abstract It was shown by static and dynamic light scattering that poly(vinyl)pyrrolidone (PVP) molecules form large intermolecular complexes (clusters) with C70 in aqueous solutions. The molecular weights and dimensions of PVP–C70 clusters increase both with the increase of fullerene content and the molecular weight of the matrix PVP. However, two different diffusion coefficients were detected by dynamic light scattering. The slow mode was explained as diffusion of large PVP–C70 clusters. The fast mode represents free PVP molecules in solution. Dimensions of clusters revealed in aqueous PVP–C70 solutions are less than that for PVP–C60 by factor of 2.5–3.

Synthesis of Branched Chemodegradable Homopolymers of N-(2-Hydroxypropyl)methacrylamide

Branched water-soluble N-(2-hydroxypropyl)methacrylamide homopolymers containing interchain urethane links were prepared. The hydrodynamic and molecular-weight characteristics of the branched homopolymers and the rate of their hydrolysis under the conditions close to those of a living body (saline, pH 7.0, 37°C) were determined.

Synthesis, Structure, and Characteristics of Ultra-High-Molecular-Weight Poly-N-methacryloyloxyethyl-N,N,N-Trimethylammonium Methyl Sulfate

Two procedures for synthesis of water-soluble poly-N-methacryloyloxyethyl-N,N,N-trimethylammonium methyl sulfate are compared. Synthesis occurred by the radical mechanism with the Co(III)-glycine system and with acid catalytic initiation. The effect of the initiator nature and the reaction conditions on the course of polymerization was studied.

Synthesis of Water-Soluble Chemodegradable N-Vinylpyrrolidone-Crotonic Acid-2-Hydroxyethyl Methacrylate Terpolymers Containing Interchain Urethane Cross-Links, as Carriers of Substances with Antimicrobial Activity

Water-soluble branched N-vinylpyrrolidone-crotonic acid-2-hydroxyethyl methacrylate terpolymers containing labile interchain urethane cross-links were prepared. Their molecular-weight characteristics were determined, and the hydrolytic stability under conditions close to those in a living body was evaluated. Polymeric salts of gentamicin were prepared from linear and branched chemodegradable N-vinylpyrrolidone terpolymers.

Directional Synthesis of Hybrid Polymers from 2- and 4-Vinylpyridines

Formation of hybrid three-dimensional structures by treatment of copolymers of 2- and 4-vinylpyridine with butyllithium, followed by grafting of tert-butyl acrylate molecules, was studied by mass-spectrometric thermal analysis and 13C NMR spectroscopy.