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A three‐state model for counterions in a dilute solution of weakly charged polyelectrolytes
Author(s) -
Kramarenko Elena Yu.,
Khokhlov Alexei R.,
Yoshikawa Kenichi
Publication year - 2000
Publication title -
macromolecular theory and simulations
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.37
H-Index - 56
eISSN - 1521-3919
pISSN - 1022-1344
DOI - 10.1002/1521-3919(20000601)9:5<249::aid-mats249>3.0.co;2-#
Subject(s) - polyelectrolyte , counterion , thermodynamics , chemistry , chemical physics , state (computer science) , polymer chemistry , chemical engineering , statistical physics , ion , physics , polymer , organic chemistry , mathematics , algorithm , engineering
In this paper we consider the influence of counterion distribution on the behavior of polyelectrolyte systems. We propose the unified model to describe and to compare the swelling and collapse properties of single polyelectrolyte chains in dilute solutions, microgel particles of various molecular masses, and (as a limiting case) macroscopic gels. A novel feature of the new approach is that we distinguish three possible states of counterions: free counterions inside and outside the polymer macromolecule and a bound state of counterions forming ion pairs with corresponding ions of polymer chains. The latter possibility becomes progressively important when macromolecules or gels shrink. In this case the formation of a supercollapsed state is possible, when all couterions are trapped and form ion pairs. On the other hand, the fact that counterions can float in the outer solution affects essentially the conformation of polyelectrolyte chains in dilute solutions of good quality where practically all counter ions can escape the space inside polymer coils and the repulsion between uncompensated charges plays an important role in the chain behavior.