The reactivity of surface modification of hydroxyapatite particles depends on their shape

The effect of hydroxyapatite (HA) particle shape on the reactivity of HA surfaces was investigated by selecting the rod-shaped (r-HA) and spherical HA particles (s-HA) to coinitiate the ring-opening polymerization of d , l -lactide (DLLA) used stannous octoate (Sn(Oct) 2 ) as the catalyst, respectively. It was found that both s-HA and r-HA could be grafted with PDLLA and the reactivity of s-HA was higher than that of r-HA according to the results from FTIR, NMR, TGA and BET method. The potential mechanism was that the shape of HA particles determined the crystal faces exposed to participate in graft reaction clarified by performing X-ray diffraction detections and Materials Studio analysis. The primary crystal faces were (211) and (112) for s-HA yet (002) and (300) for r-HA. These findings suggested that the shape of HA particles might influence their reactivity, which might provide a new way to improve the graft ratio of polymers so as to prepare HA/polymer composites with strong interfacial strength by selecting or designing the shape of the HA particles.