Naslov
Ion–specific and Charge Effects in Counterion Binding to Poly(styrenesulfonate) Anion

Autori
Požar, Josip ; Bohinc, Klemen ; Vlachy, Vojko ; Kovačević, Davor

Izvornik
Physical Chemistry Chemical Physics (1463-9076) 13 (2011), 34; 15610-15618

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
polyelectrolytes; poly(sodium 4-styrenesulfonate); microcalorimetry; potentiometry; Ion solvation; enthalpy

Sažetak
In order to obtain a deeper insight into effects occurring when electrolyte solution is added to solution of a strong polyelectrolyte, the microcalorimetric and potentiometric titrations of poly(sodium 4-styrenesulfonate) (Na+PSS−) solution with different alkali, earth–alkali and tetraalkylammonium nitrate, perchlorate and chloride solutions were performed. From the calorimetric titrations the differences in sign and magnitude of enthalpy change upon addition of various electrolytes were observed depending on the salt used. Potentiometric titrations using sodium ion selective electrode have revealed that addition of electrolyte is accompanied by the increase in sodium activity until a certain critical value is reached, which seems to be the consequence of counterion substitution on the polyelectrolyte chain. In the case of addition of lithium and sodium salts the experimental results for ΔH of mixing can be qualitatively correctly explained by the Poisson–Boltzmann and Monte Carlo calculations based on the continuum solvent models. This is not the case for the mixtures with KNO3, RbNO3 and CsNO3 salts. The results suggest that the ion–specific effects, associated with the changes in water structure, have to be taken into account when thermodynamic properties of polyelectrolytes in solution are concerned. The calorimetric results imply that the enthalpically observed cation speci ficity for binding to poly(styrenesulfonate) group could be correlated with corresponding cation hydration enthalpies. The counterion substitution of sodium with divalent cations was found to be endothermic, which is in qualitative agreement with the electrostatic theory.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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