Biomimetic synthesis of oriented hydroxyapatite mediated by nonionic surfactants.

Highly oriented organization of hydroxyapatite (HAP) nanorods was achieved through a simple reflux method using mixtures of triblock copolymer pluronic P123 and tween-60 as the mediated agents. Raft-like organized complexes were prepared when the nanorods were only directed by the mixed surfactants. Bundles of nanorod-like HAP crystals were obtained when urea was used as the cosurfactant. These HAP nanorods with a large amount of uniform 4 nm worm-like mesopores were arranged in parallel to each other along the c axis of HAP. The raft-like complexes might be mediated by the reverse lamellar micelles. And the added urea transformed the reverse lamellar micelles into hexagonal ones due to its association with the surfactant molecules by hydrogen bonds, resulting in the formation of bundles of nanorod-like HAP crystals. The regulation of the oriented HAP complexes in morphology extends the understanding of biomineralization and permits controllable design of biomimetic materials. In addition, the c-axis oriented raft-like HAP complex has great potential in selective bio-absorption and separation.