An infrared study on Langmuir-Blodgett films of 14,15-bis(hydroxyimino)-13-thiaoctacosane

Abstract

The Langmuir-Blodgett (LB) films of 14,15-bis(hydroxyimino)-13-thiaoctacosane (TOC) on aluminium plated substrates were investigated using Fourier transform infrared (FTIR), grazing angle (GAIR) and horizontal attenuated total reflectance (HATR) techniques. The LB films of TOC can be transferred onto the solid substrate successfully. The molecular structure of LB films was analysis by comparing the GAIR and HTAR spectra. The intense bands at 2848 and 2918 cm(-1) are assigned to symmetric nu (s)(CH2) and asymmetric nu (a)(CH2) stretching vibrations of methylene groups. These peaks suggest that the alkyl chains in TOC are nearly in all-trans conformational state. The presence in the infrared spectra of several bands due to the methylene wagging and twisting modes and of the splitting of the bands due to the methylene scissoring mode at 1467 and 1459 cm(-1) and the CH2 rocking mode at 720 and 731 cm(-1) also indicates that in films of TOC alkyl chains are in the all-trans conformation and packed in either an orthorhombic or a monoclinic structure with an orthorhombic subcell containing two mutually orthogonal molecules. Another conclusion presented in this paper that the alkyl chain tilt, which is the angle between the axis, which bisects the C-C bonds and the surface normal, was quite large by comparing the GAIR and HATR spectra. (c) 2005 Elsevier B.V. All fights reserved.