Surface freezing in n-alkane solutions: The relation to bulk phases

Surface freezing (SF) was investigated in tricosane-dodecane alkane solutions as a function of temperature (T) and molar concentration of tricosane (Formula presented) using surface tension and synchrotron x-ray surface diffraction techniques. A crystalline SF monolayer, having a rotator (Formula presented) structure, was found to exist for (Formula presented) and (Formula presented) The extended temperature range allowed to determine the linear-expansion coefficient of the SF monolayer, (Formula presented) A simple thermodynamical model based on the theory of ideal solutions is shown to account well for the (Formula presented) dependence of the SF temperature (Formula presented) The study shows that the temperature range of existence of the surface frozen layer at each (Formula presented) the (Formula presented) range over which SF is observed, and the bulk solidification behavior, are intimately related. All are determined by the rotator-liquid dissolution line (Formula presented)