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Title
Japanese: 
English:A Conformation and Orientation Model of the Carboxylic Group of Fatty Acids Dependent on Chain Length in a Langmuir Monolayer Film Studied by Polarization-Modulation Infrared Reflection Absorption Spectroscopy 
Author
Japanese: 室 麻衣子, 伊藤 雄樹, 長谷川 健.  
English: Maiko Muro, Yuuki Itou, Takeshi Hasegawa.  
Language English 
Journal/Book name
Japanese: 
English:J. Phys. Chem. B 
Volume, Number, Page Vol. 114        pp. 11496-11501
Published date Sept. 2010 
Publisher
Japanese: 
English:The American Chemical Society 
Conference name
Japanese: 
English: 
Conference site
Japanese: 
English: 
DOI https://doi.org/10.1021/jp105862q
Abstract The conformation of the carboxylic group of fatty acids in a Langmuir (L) monolayer film on water is described in relation to the aggregation property of the hydrocarbon chain. Polarization-modulation infrared reflection absorption spectra (PM-IRRAS) of L films of heptadecanoic acid (C17), octadecanoic acid (C18), and nonadecanoic acid (C19) exhibit systematic spectral changes in both the CsH and CdO stretching vibration regions. Through a stabilization analysis of the L films at a high surface pressure, the C19 L film has been found outstandingly stable exhibiting no film shrink, while the other two compounds exhibit a large shrink at high surface pressure. By taking into account the uniquely high aggregation property of the hydrocarbon chains of C19, the three major bands arising from the CdO stretching vibration mode propose three types of molecular conformations about the carboxylic group, which are elucidated by a balance of the hydration of the carboxylic group, the chain length of the hydrocarbon chain, and the surface pressure.

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