IN-SITU SUM-FREQUENCY SPECTROSCOPY OF SODIUM DODECYL-SULFATE AND DODECANOL COADSORBED AT A HYDROPHOBIC SURFACE

The adsorption of sodium dodecyl sulfate (SDS) and dodecanol from solu tions of the pure and mixed surfactants onto hydrophobic substrates wa s studied by infrared-visible sum-frequency spectroscopy. Pure films o f dodecanol were found to be more densely packed and to contain fewer gauche defects than those of SDS. A marked increase in the conformatio nal order of the SDS occurred upon the coadsorption of dodecanol. This effect was only observed below the critical micelle concentration (cm c)-above the cmc, the dodecanol only absorbed weakly and resided mainl y in the SDS micelles.