engleski

The effect of cation type, ionic strength and temperature on the complexation between polyallylammonium cation and polystyrenesulfonate anion

The reaction between polyallylammonium cation and polystyrenesulfonate anion was investigated in alkali-metal chloride (MCl, M = Li, Na, K, Rb, Cs), sodium perchlorate and tetraethylammonium chloride solutions by means of microcalorimetry, potentiometry, DLS and spectrophotometry. The influence of ionic strength, temperature and addition order on the course of interpolyelectrolyte neutralisation was examined. At lower molar ratios of positively to negatively charged monomers and at 25 °C primary polyelectrolyte complexes were formed. Close to equivalence their flocculation occurred. The complexation was predominantly entropically driven, however a correlation between obtained reaction and cation hydration enthalpies was noticed. The composition of the precipitates at equimolar monomer ratio in chloride salt solutions did not significantly depend on the addition order up to 1.0 mol dm-3 salt concentration. In contrast, the ratio of oppositely charged monomers in precipitates prepared in NaClO4 (c / mol dm-3 ≥ 0.5) was affected by the addition order in a wide temperature range. The increase in electrolyte concentration and the decrease in temperature led to more pronounced asymmetric neutralisation. The equilibrium establishment in NaClO4(aq) proceeded extremely slowly. Even at high perchlorate concentrations the final reaction product was virtually insoluble polysalt.

polyelectrolyte complexation ; microcalorimetry ; ion-specific effects ; ion hydration

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