Thermodynamics and X-ray studies of 2-alcohol monolayers at the air water interface

We investigate monolayers of 2-alcohols (2-C9 to 2-C16) obtained by placing a drop of pure alcohol at the water surface. These alcohols are chiral molecules and we study the racemic mixtures. By ellipsometry and surface tension measurements we are able to characterize the 2D crystallization-melting transition with temperature. We find a first order transition. Using X-ray under grazing incidence we show that the racemic mixture crystallizes at 2D on a hexagonal cell. We find a parity effect on the lateral pressure at the transition and on the stability of the Bragg peak. We compare all results with those observed for 1-alcohols.