| Abstract
| - Infrared external reflection (IER) spectra of sodium dodecyl sulfate (SDS) monolayers at the air−solutioninterface and infrared transmission spectra of the corresponding aqueous solutions were measured at variousSDS concentrations and temperatures. A comparison between the spectra of adsorbed monolayers and bulksolutions revealed that the conformational order of the SDS alkyl-chain at the air−solution interface improvedwith increasing the SDS concentrations, up until the saturation adsorption, and that the conformational orderof the adsorbed SDS monolayer was higher than those of monomers and micelles. In addition, below theKrafft point temperature, the adsorbed SDS was maintained in the liquid crystal state, while SDS in the bulksolution was in the crystalline state. Furthermore, the SDS adsorption density was evaluated based on theIER band intensities of the insoluble monolayer of tridecanoic acid with an identical alkyl chain length toSDS.
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