Effect of mixed sol-gel precursors on the metal-oxo phase within a UV-curable silicone hybrid material

An inorganic hybrid material was produced using a polysiloxane binder and metal-oxo-clusters which were derived from sol-gel precursors. The continuous phase is composed of an elastomeric polysiloxane functionalized with cycloaliphatic epoxide groups. Pendant alkoxy silane groups serve as a coupling agent to form a network between the metal-oxo-clusters and the crosslinked polysiloxane. Methyl, cyclopentyl, and cyclohexyl substituted polysiloxanes were formulated with a variety of sol-gel precursors (tetraethylorthosilicate oligomers, titanium(IV) iso-propoxide, zirconium(IV) propoxide, and zinc acetate). Phase-modulated FT-IR, X-ray photoelectron spectroscopy, solid state Si-29 NMR, 3 and solid state C-13 NMR were used to investigate the internal structure of the mixed metal-oxo/silicon-oxo colloids prepared within the cured polysiloxane matrix. Results indicate that the cycloaliphatic groups inhibit the complete hydrolysis and condensation of the pendant triethoxysilane group and reaction of the sol-gel precursors. Analysis also indicated that the metal-oxo-clusters were comprised of mixed species of sol-gel precursors resulting in hetero-bonded (Si-O-Metal) colloids.