Katja Arh and Ciril Pohar
Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, SI – 1000 Ljubljana, Slovenia
The enthalpies of dilution (DHD, c -> 0.002 mol/dm-3) of aqueous solutions of 3,3- 4,5- 6,6- and 6,9- ionenes with Br- and Cl- counterions, respectively, have been measured over a broad concentration range at 25°C. The enthalpies of dilution show rather big dependence on the kind of the counteriion, as well as large dependence on the charge density of ionenes. For 3,3- and 4,5- types dilution effects are endothermic, while for 6,6- and 6,9-ionenes are exothermic in the low concentration range and become endothermic in more concentrated solutions. The concentration dependence of the enthalpy of dilution of ionene solutions were compared with predictions of electrostatic cell theory. An agreement between theory and experiment was found only if the effects of specific interactions were included in the calculations.