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Interaction between oppositely charged polyelectrolytes in aqueous solution
Author(s) -
Oppermann W.,
Schulz Th.
Publication year - 1990
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19900390125
Subject(s) - polyelectrolyte , counterion , stoichiometry , enthalpy , chemistry , aqueous solution , molar mass , monomer , cationic polymerization , polymer chemistry , inorganic chemistry , thermodynamics , polymer , organic chemistry , ion , physics
Oppositely charged polyelectrolytes interact in solution, forming polyelectrolyte complexes, which often appear as gel‐like precipitates. This kind of complex formation was studied by means of calorimetric and rheological measurements. The enthalpy effects, though being fairly small, give some information about the binding strength of counterions to the macroion. We studied the system poly(p‐styrene sulfonate)/poly(trimethylammonium‐2‐ethyl methacrylate) (PSS‐PTMA), varying systematically the low molar mass counterions of PSS. In every case, the maximum of enthalpy was found around a 1:1 (mol:mol monomer units) composition of the complexes, with the shape of enthalpy versus composition‐curve indicating a stoichiometric interaction. The maximum enthalpy decreased with increasing atomic mass of the counterion when the alkaline metal salts of PSS were used and no change was made on the side of the cationic polyelectrolyte. The salts of the alkaline earth metals gave a distinctly higher enthalpy. On the contrary, viscosity measurements showed a very broad minimum as a function of composition, indicating that the formation of non‐stoichiometric complexes is also occurring. The conclusion of these observations is that the complex formation is stoichiometric with respect to the monomeric units, but not necessarily stoichiometric with respect to the entire macromolecules.