Fluctuation-Stabilized Surface Freezing of Chain Molecules

Abstract

We propose a fluctuation-based entropic scenario for the explanation of surface freezing in alkanes and other liquids of chain molecules. Our model is based on the notion that strong fluctuations along the molecular axis of uniaxially ordered stretched chains can exist in a solid monolayer on top of a liquid phase, and provide sufficient entropy to stabilize it against the formation of a bulk rotator phase. We show that the phenomenon can exist only in a restricted range of molecular weights, and calculate the molecular weight dependences of the temperature range in which it is observed and of the correction to the surface tension.