FTIR Studies of C₃₀Self-Assembled Monolayers on Silica, Titania, and Zirconia

Abstract

The conformational order of alkyl chains in four different C30 self-assembled monolayers (SAMs) has been examined using Fourier transform infrared spectroscopy. The C30 SAMs used in the present study were prepared by reacting C30H61SiCl3 with the humidified surfaces of zirconia, titania, and two different silica gels. The conformational order of the alkyl chains that are attached to the solid substrates is derived from the analysis of well-known conformation-sensitive IR regions, that is, CH2 symmetric and antisymmetric stretching modes as well as CH2 wagging bands. The CH2 symmetric and antisymmetric stretching band positions provide a qualitative measure of the conformational order. The CH2 wagging bands are used to determine the relative amounts, that is, integral values over the whole chains of kink/gauche-trans-gauche, double-gauche, and end-gauche conformers in the alkyl chain regions. The results derived from the present IR data analysis demonstrate that the substrate plays an important role for the conformational order of alkyl chains that are attached to inorganic oxide surfaces. C30 SAMs on titania are found to possess a higher degree of conformational order as compared to C30 SAMs on zirconia and silica.