Derby in the polyelectrolyte jungle

Significance 

Studies involving polyelectrolytes have attracted significant attention amongst researchers. This can be attributed to their wide range of applications in various fields and processes. Unfortunately, the organization of charged macromolecules has not been fully explored due to the varying polyelectrolyte chain sizes in different solutions. The sizes depend on the strength of the particular solution. Generally, the strength of the electrostatic interactions results in their widespread over long distances. To this note, various research works have investigated the contribution of electrostatics to the segment length of polyelectrolytes. For example, in low ionic strength solutions, the large polyions sizes have been assumed to be due to the impact resulting from the intermolecular long-range interactions.

Recently, the total persistence length of polyelectrolytes chains has been described as the sum total of the electrostatic and bare components. However, the main features of a polyelectrolyte chain comprise of the hydrophobic or hydrophilic property of the bare chain as well as the charge density. Therefore, charged copolymers based on bare hydrophilic chains are very crucial in the evaluation of pure electrostatic interactions and their effects on the chain sizes. This is because they remain soluble in water for the entire range of the charge densities. For bare hydrophobic chains, the competition between the hydrophobic interactions and electrostatics determines the behavior of the low charged macromolecules.

Dr. Georges Pavlon, Olga Dommes, Dr. Olga Okatova, Irina Gavrilova and Professor Evgenii Panarin at Institute of Macromolecular Compounds, Russian Academy of Sciences investigated the hydrodynamic sizes and volumes of macromolecules of copolymers based on hydrophilic poly(N-methyl-N-vinylacetamide) in water solution. They used polymer chains of similar contour lengths and different low or moderate charge densities. They purposed to determine the dependence and trends of the average charge density on the viscosity at low ionic strength. Consequently, they compared the polyions sizes in salt-free solutions with the degree of charge in the entire range of the charge density. Eventually, they established a new parameter to describe the correlation between the charge average density of the bare linear chain and the statistical hydrodynamic length and volume of the segment. Their research work is published in the journal, Physical Chemistry Chemical Physics.

From the proposed parameter that is represented as lqq/Abare, a ratio of the average distance between the neighboring charges along the chain to the statistical segment length of a non-charged homologue, the authors observed that it indicated regions dominated by electrostatics short-range or long-range interactions. For instance, the three ranges observed were lqq/Abare>2 indicating a moderate increase in viscosity, lqq/Abare<2 indicating a sharp increase in viscosity and lqq/Abare <0.7 indicating saturation level with invariable intrinsic viscosity.

According to the authors, the first range represented an increase in the hydrodynamic volume due to the increase in the electrostatic long-range contribution to the chain dimensions. Consequently, the third range represented the adverse effects of the contributions of the short-range interactions. However, the intermediate range takes into consideration both the contributions of the short and long-range interactions with first increase in the charge density.

About the author

Dr. Sci. Pavlov Georges M. is a Leading Researcher in the Institute of macromolecular compound, Russian Academy of science and in the Saint Petersburg University (department of biophysics and polymer science).

His qualification works were master thesis: “Investigation of hydrodynamic characteristics of macromolecules of polypropylene sulfide and DNA.” (Leningrad State University, Department of Physics, 1965), PhD thesis: “Optical and hydrodynamic properties of homologous series of graft copolymers.” Supervisors: Professor Tsvetkov V. N., and PhD Magarik S. Ya. (Institute of macromolecular compounds of the USSR Academy of Sciences, 1975 ) , and Dr. Sci. thesis; “ Molecular hydrodynamics and optics of natural and synthetic polysaccharides.” (Sankt-Petersburg State University, Department of Physics, 2004)

His directions of scientific activity are following: Investigation of the properties of functional synthetic and biological macromolecular compounds, establishing the relationship between the chemical structure and the properties of macromolecules; Study of the properties of polyelectrolytes / polyelectrolyte complexes in the extremely wide range of ionic forces; Macromolecules of complex topology (comb-shaped, star-shaped, dendrimer, hyperbranched, and supramolecular structures); Influence of molecular characteristics of polymers on the properties of their films at the interface; Methodology of molecular hydrodynamics (velocity sedimentation, translational diffusion, viscous flow of dilute solutions) and birefringence of polymer films and solutions.

During his work at the University under the supervision of Pavlov G.M. the Master graduation theses on the Department of Polymer Physics were completed and successfully defended by 30 students. He is supervisor of several PhD thesis and PhD students.

Pavlov is author/coauthor of about 200 publications in international and Russian scientific journals. He is the author of several review chapters in monographs of publishing houses Elsevier, Springer, Taylor&Francis.

ResearcherId: K-8194-2013
ScopusId: 7101978332
ORCID: 0000-000108897-769X

About the author

Ms. Olga A. Dommes, junior researcher, Ph.D student.

In 2012 graduated from the St.-Petersburg State University, Physical Faculty, Department of Molecular Biophysics.

Since 2013 she works in the Institute of Macromolecular Compounds of Russian Academy of Sciences, Analytical laboratory. The topic of Ph.D thesis is “Short-range and long-range electrostatic interactions in chains of linear polyelectrolytes based on N-methyl-N-vinyl acetamide”.

She studies macromolecules in solutions, performs experimental measurements using methods of molecular hydrodynamics: intrinsic viscosity, translational diffusion, velocity sedimentation. Viscosity measurements of polyelectrolytes are carried out in a wide range of ionic strength, including pure water solutions and titration experiments. She attends international conferences and is coauthor of several scientific papers.

Main problems under investigation:

  • the determination of correlation between the chemical structure of the macromolecules and their properties (molecular mass, size, conformation) in dilute solutions,
  • the study of intrachain electrostatic interactions in polyelectrolyte solutions at low ionic strength

Subjects and objects of the research:

  • hydrodynamic properties of the polymer molecules of different architecture in different solvents for determining the macromolecular conformation.

ResearcherId: I-2950-2017
ScopusId: 55996301800
ORCID: 0000-0003-3409-5397
e-mail: [email protected]
www.macro.ru

About the author

Dr. Olga V. Okatova, senior researcher, Ph.D.

Institute of macromolecular compounds of Russian Academy of Sciences, Analytical laboratory.

Graduated from the St.-Petersburg State University, Physical Faculty, Department of Polymer Physics.
She is a skillful experimenter in the sedimentation and diffusion analysis of macromolecules in solution, the coauthor of more than120 scientific papers in international and Russian journals.

Main problems under investigation:

  • the determination of correlation between the chemical structure of the macromolecules and their properties (molecular mass, size, chain flexibility) in dilute solutions,
  • the determination of the conformations of charged macromolecules in solutions.

Subjects and objects of the research:

  • hydrodynamic properties of the polymer molecules of different architecture in different solvents (including strong inorganic acids) for determining the macromolecular conformation.

ResearcherId: I-2583-2017
ORCID: 0000-0002-7348-4320
e-mail: [email protected]
www.macro.ru

About the author

Irina I. Gavrilova, researcher.

Institute of macromolecular compounds of Russian Academy of Sciences, Laboratory of Hydrophilic Polymers.

Graduated from the Leningrad North-West University, Chemical Faculty, Department of Organic Synthesis.

She is a skilled chemist-synthetic. The scope of her interests is synthesis of water-soluble polymers based on N-vinyl amides and functional vinyl and allyl monomers, and the study of the reactivity of functional groups of polymers. She is coauthor of more than120 scientific papers in international and Russian journals.

e-mail: [email protected]

About the author

Evguenii Panarin, Corresponding Member of Russian Academy of Sciences, Doctor of Chemistry, Professor, Head of the Laboratory of Hydrophilic Polymers in the Institute of Macromolecular Compounds of Russian Academy of Sciences (IMS RAS), Scientific Leader of the Institute, during 1987-2015 Director of IMS RAS.

Main Activities:

E. Panarin substantiated the ways of directed modification and correction of the biological activity of medicinal substances by polymers. He developed methods for synthesizing multi-purpose water-soluble polymers-carriers with a wide range of functional groups that ensure the addition of biologically active substances to the macromolecule by a given type of bond. These polymers have been proposed as models of some biopolymers, as well as they were used as carriers for targeted delivery of biologically active substances (hormones, antibiotics, enzymes, antiseptics, DNA, etc.) to a given target organ.

Among them, the fundamental importance have the study of the mechanisms of chemical reactions of synthesis and conversion of polymers, the chemical and enzymatic synthesis of vinyl saccharides, obtaining water-soluble polymers based on N-vinyl amides and functional vinyl and allyl monomers, and the study of the reactivity of functional groups of polymers. Panarin E. was the first who established the relationship between the chemical structure and the own biological activity of functional water-soluble polymers. As a result of these studies, a new class of polymeric substances exhibiting antimicrobial, antiviral, antitumor, immunomodulating, growth-stimulating and other types of activity was discovered. Panarin E. formulated the principles and developed the methods for constructing nanostructured polymer systems with polyfunctional biological activity, and new drugs were created.

The results of his basic research Panarin E. uses for solving the applied problems. Under his leadership, a set of technologies for production of new water-soluble polymers and polymer drugs were developed and implemented by the domestic industry.

Panarin E. is the Honored Inventor of the Russian Federation, having many (100) Russian patents and the author/coauthor of more than 800 scientific papers, including the monographs “Antimicrobial Polymers”, “Excited States in Polymer Chemistry”, “Polymers – Carriers of Biologically Active Substances”, textbook “Polymers in medicine and pharmacy”.

ResearcherId: P-1767-2016
ORCID: 0000-0002-7005-5838
e-mail: [email protected]
www.macro.ru

Reference

Pavlov, G., Dommes, O., Okatova, O., Gavrilova, I., & Panarin, E. (2018). Spectrum of hydrodynamic volumes and sizes of macromolecules of linear polyelectrolytes versus their charge density in salt-free aqueous solutions. Physical Chemistry Chemical Physics, 20(15), 9975-9983.

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