Preparation And Modification Of Nano-hydroxyapatite

Due to the special nature of the chemical composition and crystal structure,Hydroxyapatite which has good biocompatibility and bioactivity, is used as the bone substitute materials in clinical studies. But n-HA has defects, which limit its clinical application, such as high brittleness, poor toughness and low biomechanical strength etc, so that it can not completely replace the human bones. Research has shown that because of small size, surface effects and other features, nano-hydroxyapatite can improve strength, toughness and biological activity. To ameliorate its property, this paper synthesized n-HA modified with PDLA on its surface. Then, Stereocomplex of PDLA-n-HA/PLLA was prepared through a mix of both. The main work of the paper is as follows:Firstly, Preparation of PEO-HAP, then, PDLA grafts it. This part of the work, a different molecular weight polyethylene glycol is reacted with phosphorus pentoxide to generate phospholipids. Then, the content of monoestery is determinedt by acid-base titration, and nanocrystal hydroxyapatite were prepared by a wet chemical chemical precipitation method, which was synthesized by mixing with Phospholipid,OH4NOCa223)(?and 424)(HPONH ?. The PDLA-n-HA was prepared by ring-opening polymerization with Sn(OCt)2 as catalyst. In this experiment, the PDLA-n-HA were characterized by NMR, IR and TG, the results show that the graft ratio of polylactic acid in nanoparticles surface reaches 8%.Secondly, Hydroxyapatite modification: This first part of the study, nanohydroxyapatite were prepared by a wet chemical precipitation method.Then, HAp modified with EG was synthesized by mixing with HDI and EG, with DBT as catalyst,Because the terminal hydroxyl groups remain active, so surface of hydroxyapatite can grafts long chain poly-lactic by lactide ring-opening using E-HAP as the initiatoracid.The materials were characterized by IR and TG, the data show: the graft ratio of polylactic acid on nanoparticles surface reaches 14%.Finally, preparation of composites(PDLA-n-HA/PLLA): First of all, synthesis of high molecular weight(Mη≈1×104)PLLA was carried out via ROP of monomer L-LA using benzyl alcohol as initiator. Then, PDLA-n-HA/PLLA hybrid materials were obtained by the stereocomplex of PDLA-n-HA and PLLA and hot press molding. The materials were characterized by NMR and Mechanical property test, the results showed that mechanical properties of Composites is excellent.