Molecular Dynamics Simulations of Langmuir-Blodgett Monolayers with Explicit Head-group Interactions

Abstract

Energy minimisation and molecular dynamics calculations have been performed for models of Langmuir-Blodgett films containing stearic acid molecules. The model includes a specific representation of the atoms and dipole moment of the carboxylic acid head-group. Simulations have been performed at head-group areas per molecule of 20.6 Ų and 21.2 Ų at room temperature. This all-atom model predicts significant conformational disorder at the torsional angle connecting the head-group to the hydrocarbon chain. The strong charge/image-charge interaction doubles the tilt of the layer over that found for the united-atom Lennard-Jones head-group. The dipoles of the head-group are alined parallel to the surface forming a two sub-lattice structure in the plane of the surface.

Key Words:

• Langmuir-Blodgett films
• stearic acid
• tilting transition