CONTROLLED CRYSTALLIZATION OF CALCIUM-PHOSPHATE UNDER STEARIC-ACID MONOLAYERS

Controlled crystallization of calcium phosphate from supersaturated solutions by using stearic add monolayers has been investigated by scanning electron microscopy, transmission electron microscopy with selected-area diffraction, and X-ray diffraction. Whereas crystallization in the absence of a monolayer results in minuscule spheric octacalcium phosphate (OCP) particles distributed randomly in the solution, the presence of organized monolayers gives rise to (0001) oriented hydroxyapatite (HAp) nuclei across the organic substrate. This result has been explained by the molecular recognition effect of the electrostatic interactions and lattice matching between the inorganic-organic interface. Subsequent growth results in OCP platelets with (010) preferred orientation on the HAp crystals due to a nearly coherent relationship existing on the interface of the two phases and suitable solution conditions.