Triblock co-polymer templating synthesis of mesostructured hydroxyapatite

Mesoporous hydroxyapatite (Ca10(PO4)6(OH)2 or HA) was synthesized using non-ionic block co-polymer pluronic F127 (EO99PO65EO99) as template. Two groups of HA samples were prepared by co-precipitation method with different concentrations of the surfactant, which were characterized by means of X-ray diffraction (XRD), small angle XRD, electron microscopes and BJH gas absorption method. It was found that the as-synthesized and calcined samples of the two groups had a typical HA crystal phase, but the particle morphologies and pore size distribution were significantly different, depending on the surfactant concentration used. When a high surfactant concentration (10 g F127/100 g distilled water) was used, the sample obtained consisted of spherical particles (∼100 nm in diameter), with a maximum distribution of pore size 58 Å. However, when the F127 concentration was 3 g/100 g distilled water, the sample with rod-like particles (∼100-300 nm in length and ∼40-50 nm in diameter) could be obtained, and a bimodal pore size distribution at 25.3 Å and 30 Å were also observed in this sample. Promising consistency between the pore sizes from BJH, TEM and small angle XRD was observed, which indicates the successful synthesis of mesoporous hydroxyapatite in current work. A possible mechanism was proposed to interpret the formation procedure of mesoporous structure.