Nonstoichiometric polyelectrolyte complexes: A mathematical model and some experimental results

Autor(en): Nordmeier, E
Beyer, P
Stichwörter: COUNTERION BINDING; degree of complexation; degree of counterion binding; DNA; IONENE; nonstoichiometric polyelectrolyte complexes; poly(acrylacid); poly(methacrylacid); POLYCATIONS; Polymer Science; POLYMERS; ultracentrifugation; viscometry
Erscheinungsdatum: 1999
Herausgeber: JOHN WILEY & SONS INC
Volumen: 37
Ausgabe: 4
Startseite: 335
Seitenende: 348
A mathematical model is presented to describe nonstoichiometric water-soluble polyelectrolyte complexes, and the predictions are compared with some experimental results. The theory is a mixture of Madelung's theory for ionic crystals and Manning's counterion condensation theory. The central parameters are the degree of complexation, phi, and the degree of counterion binding, theta. All other quantities are known in principle. It is found that there is a competition between complexation and counterion binding. When phi is large, theta is small, or vice versa. The degree of complexation, phi, depends sensibly on the concentration, c(s), of the added low molecular salt, the polyanion chain length, N, and the dielectric constant, epsilon, of the solvent. There exists a critical salt concentration, c(s,c), at which the complexes salt out and where for c(s) > c(s,c) the complexes dissociate back into their single strands, the polyanions, and polycations. Further, phi is larger the smaller the polyanion length and the smaller the solvent dielectric constant are. To prove these predictions we have formed nonstoichiometric complexes between IONENE and PAA and IONENE and PMAA, respectively. The degree of complexation was determined by ultracentrifugation and checked by viscometry. The accord found between theory and experiment is both qualitatively as well quantitatively quite well. (C) 1999 John Wiley & Sons, Inc.
ISSN: 08876266
DOI: 10.1002/(SICI)1099-0488(19990215)37:4<335::AID-POLB7>3.3.CO;2-N

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