Heterogeneous Nucleation of Dicalcium Phosphate Dihydrate on Modified Silica Surfaces.

Heterogeneous nucleation of dicalcium phosphate dihydrate, CaHPO4•2H2O (DCPD) was studied on untreated planar fused silica and on three modified silica surfaces: octadecylsilyl (OTS) modified silica, human serum albumin treated OTS silica, and UV-oxidized 3-mercaptopropyltriethoxysilyl (MTS) modified silica. The supersaturation ratio of calcium and phosphate solution with respect to DCPD was kept below ~10. The nucleated crystals were observed 24 hours and one week after initial contact between supersaturated solutions and substrate surfaces using bright field and reflectance interference contrast microscopy. No DCPD crystals nucleated on albumin-treated OTS-silica. Majority of the DCDP crystals formed on the other modified silica surfaces appeared to be morphologically similar irrespective of the nature of nucleating substrate. Reflectance interference contrast microscopy provided a proof that the majority of the crystals on these substrates do not develop an extended contact with the substrate surface. The images showed that the most extended contact planes were between the DCPD crystals and MTS modified silica surface. The crystals nucleated on OTS-treated and untreated silica surfaces showed only few or none well-developed contact planes.

Alkenyl and alkenoyl amphiphilic derivatives of D-xylose and their surfactant properties.

Unsaturated fatty alkyl xylosides and the corresponding 1-O-acyl esters were prepared. Critical micellar concentrations, surface tension areas per molecule and foaming value of some of these new amphiphilic compounds have been determined.

Neutral pentosides surfactants issued from the butadiene telomerization with pentoses: preparation and amphiphilic properties.

Interfacial properties of octadienyl pentosides prepared by the palladium-catalyzed telomerization of butadiene with free pentoses have been evaluated and compared to those of mixtures issued from the autoclaving process.