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Thiol-functionalized nanobuilding blocks (NBBs) were synthesized from 3-mercaptopropyltrimethoxysilane by using the in situ water production (ISWP) process in which the water needed to hydrolyze the precursor was provided by means of an esterification reaction. In the present study the reaction between 1-propanol and chloroacetic acid was used. Whereas the growth of the Si oligomers was followed at room temperature and 100 °C using 1D 29Si and 2D 1H-29Si heteronuclear single quantum correlation (HSQC) NMR spectroscopic experiments, the amount of water delivered along the process was followed by means of 1H NMR spectroscopy. The results show a good correlation between the evolution of the degree of condensation and the amount of water produced in situ. They also point to the preferential formation of cagelike structures and the narrowing of the species distribution over long reaction times. The average size of the growing oligomers was estimated from their diffusion coefficient, which was measured by means of 1H diffusion-ordered NMR spectroscopy (DOSY NMR). Like gel permeation chromatography, DOSY NNR showed a plateau between 70 to 100 hours in the growth of the oligomers, a time at which, according to 29Si NMR spectroscopy, the well-defined octakis(3-mercaptopropylsilsesquioxane) is the major species. [ABSTRACT FROM AUTHOR]

Abstract: Hybrid polymer–yttria–zirconia xerogels have been used to prepare freestanding and crack free cubic yttria-stabilized zirconia (YSZ) films. Depending on the final ceramic properties, these materials could find application as components in solid oxide fuel cells. Different types of organic and bioorganic molecules such as albumin, starch, sucrose, dextran, carboxymethylcellulose, and polyvinyl alcohol, have been studied in order to prepare polymer–oxide nanocomposites. The reason for adding a polymer to a sol–gel-derived inorganic network stays in avoiding cracks formation during the pyrolysis process, which converts the preceramic into the ceramic material. Polymers behave as stress relaxing agents and allow obtaining dense and crack free final ceramics. The differences in polymer chemical structure and solubility impose variable synthesis procedures, and limit the availability of suitable yttria precursors. We present here a study concerning the influence of different polymers on the microstructural properties of yttria–zirconia films. Thermogravimetric analyses (TGA), SEM, XRD, N2 sorption and density measurements have been used to characterize the polymer-to-ceramic transformation and the final ceramic materials. [Copyright &y& Elsevier]