Abstract:

We have investigated the growth of hyperbranched polyglycidol films, and their subsequent reaction with a transition metal coordination complex, pentakis(dimethylamido)tantalum, Ta[N(CH₃)₂]₅ using ellipsometry, contact angle measurements, atomic force microscopy and X-ray photoelectron spectroscopy (XPS). Up to thicknesses of approximately 150 Å, the growth of polyglycidol is approximately linear with reaction time for growth activated using either sodium methoxide or an organic superbase. The reaction of Ta[N(CH₃)₂]₅ at room temperature with these layers depends strongly on their thickness—the amount of uptake of Ta by the surface increases with the thickness of the organic layer, and thicker films also lead to more extensive ligand exchange reactions (with the R-OH groups), with as many as 4 ligands being lost on the thicker organic films. Ta penetrates the surface of all films examined (thicknesses 30−84 Å), but the average depth of the penetration is nearly independent of the thickness of the organic film, and it is ~15−25 Å. Modification of the polyglycidol with an aminoalkoxysilane introduces a significant fraction of -NH₂ termination in the organic layer. Reactions of this layer with the Ta complex are quite different than those on an unmodified layer—now on average only a single ligand exchange reaction occurs, while on the unmodified surface as many as four ligands are exchanged.