Effect of poly(sodium 4-styrene-sulfonate) on the crystal growth of hydroxyapatite prepared by hydrothermal method

Hydroxyapatite (HA) crystals with different morphologies were synthesized by hydrothermal method, using Ca(NO3)2.4H2O and (NH4)3PO4.3H2O as raw materials and poly(sodium 4-styrene-sulfonate) (PSS) as the template. The crystals from above preparation procedure were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscope (FT-IR), transmission electron microscope (TEM), thermogravimetry analyzer (TG) and UV-Vis diffuse reflectance spectra (UV-Vis). The results show that PSS concentration and the hydrothermal temperature play key roles in controlling the morphology of HA crystals. At certain temperature, the obtained HA transformed from fibre-like to rod-like with the increasing of PSS concentration. At certain PSS concentration, the shape of obtained HA varied from rod-like to prism-like when the temperature is increased. And the aspect ratio of HA crystal decreases with the increasing of PSS concentration and hydrothermal temperature. The possible formation mechanism of different morphologies of HA crystals is also discussed in this paper.