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 pl acing a drop of pure alcohol at the water surface. These alcohols are chiral molecules and we study the racemic mixtures. By ellipsometry an d surface tension measurements we are able to characterize the 2D crys tallization-melting transition with temperature. We find a first order transition. Using X-ray under grazing incidence we show that the race mic mixture crystallizes at 2D on a hexagonal cell. We find a parity e ffect on the lateral pressure at the transition and on the stability o f the Bragg peak. We compare all results with those observed for 1-alc ohols.