Substituent Effects at the Benzyl Position and Aromatic Ring of Silane-Coupling Agents Containing 2-Nitrobenzyl Esters on Photosensitivity and Hydrophobic Surface of a Self-Assembled Monolayer (SAM)

Silane-coupling agents with 2-nitrobenzyl esters containing alkyl substituents at the benzyl position and alkoxy and/or fluoroalkoxy groups of the aromatic ring were synthesized to prepare a self-assembled monolayer (SAM) on quartz glass, silicon wafer and thermally oxidized silicon wafer. The resulting photosensitive SAMs before and after photoirradiation were characterized by contact angle measurement, UV spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray reflectivity (XRR). Photosensitivity of the SAM was influenced by substituents at the benzyl position and aromatic ring as well as the irradiation conditions in air or solution and substrates employed. Silane-coupling agents with bulky substituent at the benzyl position and double fluoroalkoxy chains are preferable in terms of the photosensitivity and hydrophobic surface.