COLLECTIVE TILT BEHAVIOR IN DENSE, SUBSTRATE-SUPPORTED MONOLAYERS OF LONG-CHAIN MOLECULES - A MOLECULAR-DYNAMICS STUDY

Molecular dynamics calculations have been used to investigate collective molecular tilt as a function of area per chain at room temperature in substrate-supported monolayers of long-chain molecules. At the highest densities the chains align approximately normal to the substrate and show a continuous increase in the collective tilt as the molecular area is increased, a finding in agreement with recent experimental results on Langmuir monolayers.1,2 An intermolecular potential which represents the methylene group as a single interaction site ("united atoms") is compared with a potential in which all atoms are included explicitly. Commonly used parameters for the united atom potential underestimate the effective diameter of the chains. © 1990 American Chemical Society.