Modification of silicon oxide surfaces by monolayers of an oligoethylene glycol-terminated perfluoroalkyl silane

Abstract

Monolayers of a new hybrid compound having two linearly coupled subunits with different functionalities were prepared on the silicon oxide and silicate-like surfaces using trichlorosilane as an anchoring group. The two subunits of the hybrid compound are a perfluorinated alkyl chain and an oligoethylene glycol chain. The synthesis of the new precursor compound, O-methyl hexaethylene glycol-icosafluorododecandiol-trichlorosilane is reported starting from commercially available triethylene glycol and perfluorododecan-1,12-diol as building blocks. The final and intermediate products were characterized by nuclear magnetic resonance (1H NMR, 13C NMR, 19F NMR and 29Si NMR), infrared spectroscopy (IR) and high resolution mass spectrometry with chemical ionization [HRMS (CI)]. The new compound was self-assembled on borosilicate glass, surface-oxidized silicon and silicon oxide surfaces. Properties of the self-assembled films as a function of the adsorption time were studied using contact angle measurements, X-ray photoelectron spectroscopy, polarization modulation infrared reflection absorption spectroscopy and scanning force microscopy. The adsorption of the hybrid silane on an atomically flat silica surface lead to the formation of poorly defined multilayer films. By contrast, the adsorption of the silane onto a less-ordered substrate resulted in the formation of a well-packed monolayer.