Web Release Date: January 19,
Adsorbed Monolayers of Mixed Surfactant Solutions of Sodium Dodecylsulfate and Cetylpyridinium Chloride Studied by Infrared External Reflection Spectroscopy
Department of Industrial Chemistry, Faculty of Engineering, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan
Received: August 22, 2007
In Final Form: October 29, 2007
Abstract:
Infrared external reflection (IER) spectra of monolayers adsorbed on mixed surfactant solutions of sodium
dodecylsulfate (SDS) and cetylpyridinium chloride were measured as a function of mole fraction of SDS
(XSDS). The alkyl chains of the surfactants in the adsorbed monolayer (Gibbs monolayer) at the air-solution
interface were in all-trans conformations in the solid state, regardless of XSDS. The adsorbed monolayers at
any XSDS had a single layer structure, except for XSDS 
0.6-0.7, which had multilayer structures. Furthermore,
the time dependency of the IER spectra revealed that the formation of the multilayer structures occurs in two
processes: a faster single layer formation followed by subsequent slower multilayer formation.
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