Mixed Ca2+/Na+(Mg2+) polyphosphates for polymer matrix filling and their solubility

Mixed cationic Ca2+/Na+(Mg2+) polyphosphates, regarded as potential biocomposite fillers, were fabricated by solid-state reactions. Most of them demonstrated low solubility (assessed also by the Glasser and Jenkins approach) from 1 +/- 0.2 g/L for Ca(PO3)(2) to 5 +/- 0.4 g/L for NaCa(PO3)(3) and 50 +/- 2 g/L for soluble phase of NaPO3. Liquid-state NMR of the soluble part of polyphosphates gave the degree of polymerization of their chains ranging from 10 to 30 for NaCa(PO3)(3) and ca. 1000 monomeric units for NaPO3.