Textured Materials Templated from Self-Assembling Media

Mineral crystals with specific surface texture have been grown by a templating mechanism from a lyotropic liquid-crystalline phase. This experimental system is important in understanding mineralization in ordered organic media, a phenomenon of importance in biology and possibly in biomaterials technology as well. The first step in the process involves the doping of a mesophase with precursor ions for the mineral phase with little disruption of the order parameter. Growth of the mineral crystals is then induced by establishing interfacial contact between mesophases doped with different precursor ions. In the system studied here, mineralization occurs at the interface as a result of diffusion of calcium and phosphate ions toward regions of lower concentration. Characterization of the precipitate formed at the interface by X-ray as well as electron diffraction, elemental analysis, and transmission and scanning electron microscopy has revealed the formation of single crystals of brushite (CaHPO₄·2H₂O) with triangular and platelike morphology. Most importantly, these crystals exhibited longitudinal striations on their surface which are believed to be due a templating effect from the liquid-crystalline phase. The striations are most likely an imprint of the preferred orientation of cylindrical molecular assemblies in the hexagonal mesophase.