Characterization of the melting–crystallization transition of alcohol monolayers at the air/water interface by polarization modulation infrared reflection absorption spectroscopy

Monolayers of 1- and 2-alcohols of varying lengths have been studied at the water surface using polarization modulation infrared reflection absorption spectroscopy. At the melting of the monolayer, we observe for all compounds a sudden increase of the conformational defects. In the liquid phase the alkyl chains contain gauche defects whereas they are all-trans in the solid phase. In addition, the chains are vertical or tilted by a few degrees with respect to the normal to the surface and the anchorage of molecules at the water surface is ensured by hydrogen bonding.