title: Hydroxyapatite surface modified by L-lactic acid and its subsequent grafting polymerization of L-lactide.
abstract: A new method of surface modification of hydroxyapatite nanoparticles (n-HA) by surface grafting reaction of l-lactic acid and ring-opening polymerization of l-lactide (LLA) was developed. Two modified HA nanoparticles were obtained: HA modified by l-lactic acid (l-HA) and HA grafting with poly(l-lactide) (PLLA; p-HA). The modified surface of n-HA was attested by Fourier transformation infrared, (31)P MAS NMR, and thermal gravimetric analysis. The results showed that l-lactic acid could be easily grafted onto the n-HA surface by forming a Ca carboxylate bond and initiated by the hydroxyl group of the grafted l-lactic acid and LLA could be graft-polymerized onto the n-HA surface in the presence of stannous octanoate. The highest grafting amounts of l-lactic acid and PLLA were about 33 and 22 wt %, respectively. The modified HA/PLLA composites showed good mechanical properties and uniform microstructure. The tensile strength and modulus of the p-HA/PLLA composite containing 15 wt % of p-HA were 67 MPa and 2.1 GPa, respectively, while those of the n-HA/PLLA composites were 45 MPa and 1.7 GPa, respectively. The elongation at the break of the l-HA/PLLA composite containing 15 wt % l-HA could reach 44%, in comparison with 6.5% of the n-HA/PLLA composites containing 15 wt % n-HA.
authors.affiliation: State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Graduate School of Chinese Academy of Sciences, Chinese Academy of Sciences, Changchun 130022, People's Republic of China.
authors.forename: Xueyu
authors.initials: X
authors.lastname: Qiu
authors.forename: Zhongkui
authors.initials: Z
authors.lastname: Hong
authors.forename: Junli
authors.initials: J
authors.lastname: Hu
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.forename: Xuesi
authors.initials: X
authors.lastname: Chen
authors.forename: Xiabin
authors.initials: X
authors.lastname: Jing
mesh_terms: D017886:Durapatite / Q000138:chemical synthesis* / Q000737:chemistry; D019344:Lactic Acid / Q000138:chemical synthesis* / Q000737:chemistry; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry; D013499:Surface Properties
chemical_list: D011108:Polymers; D019344:Lactic Acid; D017886:Durapatite