Conformation of self-assembled organic layer on the electrically polarized hydroxyapatite ceramics in nonaqueous solution

The conformation of organic compound deposited on hydroxyapatite (HAp) ceramics was manipulated by their surface charge induced by electrical polarization. The sintered HAp ceramics were electrically polarized in a d.c. field at 400 °C. The organic layers on the HAp ceramics were deposited from a toluene solution of phenyltrichlorosilane (PTCS). The results of contact angle measurements and IR spectroscopy clarified the organic layer containing the fragments of PTCS. The amount of the obtained layer on the positively charged surface was larger than those on the negatively charged and nonpolarized surfaces. The thickness of the layer on the nonpolarized surfaces was thinner than those on the polarized surfaces, based on the depth profiles of Ca2p and Si2p. Although the deposition prepared on the nonpolarized HAp surfaces from the PTCS solution was supposed to be a self-assembled layer including of phenyl–Si bond, the layers on the polarized HAp were aggregated irregularly. Consequently, the HAp ceramic surface charge induced by the polarization altered the electrostatic interaction to the organic compounds in nonaqueous system.