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 29Si NMR, and solid state 13C 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[BOND]O[BOND]Metal) colloids