In the present paper we study the effect of complexation in linear negatively charged polyelectrolytes with different alkali ions. With combination of IR-spectroscopy, X-ray diffraction and nanocalorimetry, we attempted to explain unusual solubility, crystallinity and thermal stability of these polymers. The increase of thermal stability and insolubility in water in series of semi-crystalline polysalts as K+ ≤ H+ <Na+ was explained by effectiveness of formation of chelating complex. Insoluble in water sodium salt shows the highest thermal stability of crystal phase up to . In contrast, well soluble in water amorphous lithium salt does not self-organize in chelating complex and is presented in ionic form.