Phase transitions at n-alkane/solid interfaces.

Abstract

The phase transition and molecular arrangement of various n-alkane/Al(2)O3 interfaces were studied using sum frequency generation spectroscopy. It was shown that a solid substrate, as opposed to air or vacuum, does not change the transition temperatures of n-alkanes from their bulk values. Two main phase transitions were observed. Solid n-alkanes, in both interface phases, lie on a substrate in a multilayer geometry with the C-C axis parallel to the interface and the molecular plane perpendicular to the substrate normal. This arrangement is different than that for monolayer systems or n-alkane/air interfaces.