New Facet in Viscometry of Charged Associating Polymer Systems in Dilute Solutions

The peculiarities of viscosity data treatment for two series of polymer systems exhibiting associative properties: brush-like amphiphilic copolymers—charged alkylated N-methyl-N-vinylacetamide and N-methyl-N-vinylamine copolymer (MVAA-co-MVACnH2n+1) and charged chains of sodium polystyrene-4-sulfonate (PSSNa) in large-scale molecular masses (MM) and in extreme-scale of the ionic strength of solutions were considered in this study. The interest in amphiphilic macromolecular systems is explained by the fact that they are considered as micellar-forming structures in aqueous solutions, and these structures are able to carry hydrophobic biologically active compounds. In the case of appearing the hydrophobic interactions, attention was paid to discussing convenient ways to extract the correct value of intrinsic viscosity η from the combined analysis of Kraemer and Huggins plots, which were considered as twin plots. Systems and situations were demonstrated where intrachain hydrophobic interactions occurred. The obtained data were discussed in terms of lnηr vs. cη plots as well as in terms of normalized scaling relationships where ηr was the relative viscosity of the polymer solution. The first plot allowed for the detection and calibration of hydrophobic interactions in polymer chains, while the second plot allowed for the monitoring of the change in the size of charged chains depending on the ionic strength of solutions

Star-Brush-Shaped Macromolecules: Peculiar Properties in Dilute Solution

Star-brush-shaped poly­(ε-caprolactone)-<i>block</i>-poly­(oligo­(ethylene glycol) methacrylate (PCL-<i>b</i>-POEGMA) macromolecules were synthesized and studied by molecular hydrodynamic methods. The values of the intrinsic viscosity, the velocity sedimentation coefficient, the translational diffusion coefficient, and the frictional ratio were obtained in acetone. Molar masses (<i>M</i>) were determined by the Svedberg relation, and the correlations between the hydrodynamic values and the molar mass were obtained in the range of 19 < <i>M</i> × 10^–3 g mol^–1 < 124. Comparison of the scaling indexes of the intrinsic viscosity and sedimentation velocity coefficient versus molar mass corresponding to the conventional four-arm stars macromolecules with that of the star-brush-shaped copolymer macromolecules shows that the star-brush-shaped PCL-<i>b</i>-POEGMA macromolecules have the more dense organization in space which is connected with their different topology in contrast to the conventional stars macromolecules. The model of the PCL-<i>b</i>-POEGMA macromolecules based on the ensemble of their hydrodynamic characteristics is discussed

Strong Linear Polyelectrolytes in Solutions of Extreme Concentrations of One–One Valent Salt. Hydrodynamic Study

Two series of highly charged linear aliphatic polymerssodium polystyrene-4-sulfonate and random copolymer of <i>N</i>-methyl-<i>N</i>-vinylacetamide and <i>N</i>-methyl-<i>N</i>-vinylamine hydrochloridewere studied in water solution without added salts and in solutions containing up to 5 M NaCl. Intrinsic viscosity in salt-free solutions was estimated by a method proposed earlier [Pavlov et al. <i>Russ. J. Appl. Chem.</i> <b>2006</b>, <i>79</i>, 1407–1412]. Molecular characteristics were obtained in 0.2 M NaCl. The polyelectrolytes were studied in more than 10-fold range of molar mass. Qualitatively, the conformational status of the polyelectrolyte chains in different ionic strength was defined with the Kuhn–Mark–Houwink–Sakurada plots normalized by the value of linear chain density. In salt-free solution both polyelectrolytes could be attributed to extra rigid chains with the statistical segment length of 650 nm for sodium polystyrene-4-sulfonate and 100 nm for copolymer chains. Such statistical segment lengths are provided by short-range electrostatic intrachain interactions and are comparable with the Debye screening length. At extremely high NaCl concentration polyelectrolyte chains became discriminated by their degree of hydrophobicity. Chains of hydrophobic nature are compacted up to preglobular state, whereas the chains of the hydrophilic nature stay in the conformation of swelling coils at the highest concentration of NaCl