Crystallization in Thin Films of N-Alkanes

Abstract

Chain molecules such as n-alkanes and their derivatives are main constituents of various synthetic and biological systems of great importance such as membranes and micelles. Thin films of the chain molecules on solid substrates are also important components of great technological importance. We here consider thin films of relatively short n-alkanes, C₁₁ and C₁₉, concentrating on their crystallization behavior on solid substrates. N-Alkanes on a substrate have two typical chain orientations either parallel or perpendicular to the substrate surface. The selection of either chain orientation in the film is expected be governed by various parameters, such as the chain length, the strength of the substrate attraction, and the commensuration of the n-alkane crystals to the substrate lattice. We first consider the effects of the strength of the substrate attraction assuming a simple structureless substrate. We then show how to treat the atomic structure of the substrate and discuss the important contributions of the commensurability of the substrate in controlling delicate epitaxial crystallization of n-alkanes onto the substrate.