Structural Characterization of Langmuir−Blodgett Films of Octadecyldimethylamine Oxide and Dioctadecyldimethylammonium Chloride. 1. Reorientation of Molecular Assemblies during the Accumulation of Upper Layers Studied by Infrared Spectroscopy

• Published in: Langmuir Vol. 15; no. 10; pp. 3595 - 3600
• Main Authors: Myrzakozha, Diyas A, Hasegawa, Takeshi, Nishijo, Jujiro, Imae, Toyoko, Ozaki, Yukihiro
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 11-05-1999
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Langmuir blodgett films; Surface physical chemistry; Quaternary ammonium compound; Molecular orientation; Non ionic surfactant; Cationic surfactant; Amine oxide polymer; Langmuir Blodgett layer; Experimental study; Structural analysis
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la9810152

One- and multilayer Langmuir−Blodgett (LB) films of octadecyldimethylamine oxide (C18DAO) and dioctadecyldimethylammonium chloride (2C18DAC) were prepared on gold- and silver-evaporated glass slides. The first and the rest of the layers were deposited by vertical dipping and horizontal lifting methods, respectively. Infrared (IR) reflection−absorption (RA) spectra were measured for the LB films to investigate the dependence of molecular orientation and structure on the number of layers and the substrates. X-ray diffraction and wetting properties were also measured for some of the films. For both C18DAO and 2C18DAC, there are remarkable changes in the 3000−2800 and 1700−1200 cm-1 regions between spectra of the one-monolayer LB films and those of the two-monolayer LB films irrespective of the substrates. In the spectra of the LB films of C18DAO on gold-evaporated glass slides, bands due to CH2 stretching modes show a downward shift by 5−7 cm-1 and their intensities become much weaker upon the deposition of the second layer on the first layer, suggesting that the hydrocarbon chain becomes ordered and perpendicular to the substrate surface. In general, the rearrangement of the molecular assemblies takes place during the accumulation of the upper layers in the multilayer LB films of C18DAO and 2C18DAC on the gold-evaporated glass slides.