A. Lex, P. Pacher, O. Werzer
Feb 19, 2008
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Chemistry of Materials
Abstract
A bifunctional molecule, trimethoxy[4-(thiocyanatomethyl)phenyl]silane (Si−SCN), bearing both a photoreactive unit, the benzyl thiocyanate group, and an anchoring unit, the trimethoxysilyl group, was synthesized. Upon irradiation with UV light of 254 nm under inert atmosphere, the benzyl thiocyanate group undergoes an isomerization reaction to the benzyl isothiocyanate. Kinetic investigations of liquid films of Si−SCN by Fourier transform infrared (FTIR) spectroscopy show that the thiocyanate is almost quantitatively consumed during illumination, but only 25–30% of isothiocyanate is formed. From the subsequent reaction with propylamine from the vapor phase, the isothiocyanate groups react to the corresponding thiourea compound. Thin layers of Si−SCN were applied to modify oxidized silicon surfaces. X-ray reflectivity measurements revealed a layer thickness of 6 nm. The above-described photochemistry also proceeds in these very thin layers as determined by FTIR spectroscopy and X-ray photoelectron spectros...