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Covalent modification of calcium hydroxy and fluoroapatite surface by grafting alkylphosphonate

Calcium hydroxyl and fluoroapatite (CaHAp and CaFAp) were prepared in the presence of the 2-carboxyletylphosphonic acid (2-CEPA), by hydrothermal method. The incorporation of phosphonic acid within the apatite structure was confirmed by powder XRD, IR and MAS-NMR spectroscopies and SSA. The X-ray powder analysis showed that the cristallinity was not affected by the presence of organic moieties. IR spectroscopy showed new vibration modes related to phosphonate groups. 31P MAS-NMR spectra exhibit new signals, assigned to the presence of organic phosphorus. Specific surface area (SSA) increases with increasing of phosphonate amount, especially for CaHAp. According to these results, a mechanism is proposed for the formation of two types of ionic interaction (-C-O-Ca) and (Ca-O-Porg).