This research is separated into two parts which are synthesis of sodium chitosan phosphate and preparation of polyion complexes between chitosan and chitosan phosphate. In the first part, sodium chitosan phosphates were synthesized by reacting chitosan with phosphorus pentoxide. Methanesulphonic acid was used as a solvent and a protective reagent for amino groups in chitosan structure. Substitution of chitosan hydroxyls by phosphate groups was confirmed by FTIR spectroscopy. The effect of phosphorous pentoxide/chitosan repeat units molar ratio to the degree of hydroxyl substitution was investigated by employing SEM equipped with energy dispersive X-ray spectrometer. The results obtained from the variation of the molar ratio from 0.1 to 2, showed that the degree of substitution increases with the phosphorus pentoxide content. In the second part, spherical particles of the polyion complexes were formed as a result from ionic interaction between positive charges of chitosan and negative charges of chitosan phosphate. The particles with ~50-100 nm in diameter possess a core-shell structure. Results from zeta potential and TEM revealed that surface charge of the complexes is possibly modified from positive to negative and vice versa by varying weight ratio of the components. Consequently, these polyion complexes are feasible for charged drug delivery applications.
