The temperature-dependent adsorption on hydroxyapatite (HAP) of the Tb complexes of two macrocyclic DOTA-like ligands containing HAP-binding phosphonate groups was studied by a radiotracer method using 160Tb as the label. One ligand (DOTP) contains four separate phosphonate groups, while the second ligand (BPPED) contains a single bisphosphonate group coupled via a phosphinate spacer group. The equilibrium isotherms were fitted by models according to Langmuir, Freundlich, Langmuir-Freundlich, Toth, and Dubinin-Radushkevich, with the Langmuir-Freundlich and the Toth models resulting in the best fits. These models take into account the energetic surface heterogeneity of HAP for the binding of the complexes, which was confirmed by the dependence of the reversibility of the adsorption on the complex concentration. The affinity of the Tb-BPPED complex toward the HAP surface was substantially higher than that of the Tb-DOTP complex. Thermodynamic parameters obtained from the temperature-dependence of the adsorption and the Van't Hoff relation showed that the adsorption of both complex types is endothermic and entropy-driven, due to dehydration of the complex and the HAP surface during adsorption. The kinetics of the adsorption were very fast, and of the tested models (pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich) only the Elovich model described the experimental data suitably. The activation energy of the adsorption was calculated by application of an Arrhenius-type relation, showing chemisorption for both complex types. Adsorption rates were reduced when HAP with larger particle size was used.

We have investigated the growth of octadecylsiloxane (ODS) self-assembled monolayers on mica. Freshly cleaved muscovite mica and octadecyltrichlorosilane (OTS) dissolved in toluene (c = 1.0 mmol/L) have been used as substrate and precursor, respectively. The water content of the adsorption solution was between 14.6 and 16.6 mmol/L. Adsorption experiments were carried out in a temperature range between 5 and 45 degrees C, and the obtained submonolayer ODS films were characterized with atomic force microscopy (AFM). Besides the morphology of the films, also information on the surface coverage has been obtained by quantitative evaluation of the AFM images. Depending on the temperature, evidence for both ordered and disordered expanded ODS phases has been found. The pronounced maximum in surface coverage--in contrast to adsorption on silicon substrates--at a temperature of about 27 degrees C and the different morphology of the submonolayer films as compared to silicon substrates could be explained in terms of a deposition, diffusion, and aggregation (DDA) model.

Hybrid TiO 2 -polysiloxane nanoparticles as well as hybrid TiO 2 -polysiloxane gels were prepared and characterized applying solvent-induced aggregation effects of titanium alkoxide-modified polysiloxane block copolymers. The functionalized polymers were prepared by the covalent attachment of coordination sites that allow the binding to metal alkoxides (M(OR) 4 ; M = Ti; R = ethyl, butyl, isopropyl). Composition and structure of the hybrid polymers were investigated by NMR and FT-IR spectroscopy. In a second step the metal-alkoxide functionalities were hydrolyzed to form the respective metal oxides. Depending on the solvent in which the hydrolysis took place, hybrid nanoparticles or gels were obtained as a result of the different compatibility of the polysiloxane blocks towards the polarity of the solvents. The formed materials were investigated by NMR, FT-IR, atomic force microscopy (AFM), electron microscopy, and dynamic light scattering (DLS).

Hybrid materials based on polysiloxanes and metal oxides (SiO 2 , TiO 2 , ZrO 2 ) were prepared by hydrosilation of allyl acetoacetate (AAA) modified metal alkoxides (M(OR) 4 ; M = Ti, Zr; R = ethyl, isopropyl) or vinyl triethoxysilane with poly(dimethylsiloxane-cohydrosiloxane) (PDMS-co-PMHS). The obtained compounds acted as single-source precursors in the sol-gel process. Various spectroscopic methods showed the complete functionalization of the polysiloxane chains with the complexes. When alcohols were used as solvents in the sol-gel process, hybrid nanoparticles were obtained, as observed by dynamic light scattering (DLS) measurements, transmission electron microscopy (TEM), and spectroscopic methods such as NMR and FT-IR.

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