Formation of ordered structure in Langmuir monolayers of semifluorinated hydrocarbons: Molecular dynamics simulations

We report the results of molecular dynamics simulations of Langmuir monolayers of a semifluorinated hydrocarbon molecule F(CF2)(12)(CH2)(18) H. Our simulations show that highly ordered structures are formed at low temperature after quenching from a random structure at high temperature. The structural formation process of the monolayer is characterized by a decrease in the gauche defects of the hydrocarbon block and an increase in the global bond-orientational order throughout the chain molecules. It is also found that the monolayer structure consists of mixed orientations for the head-group-free F(CF2)(12)(CH2)(18) H molecule, with a slightly larger fraction for a hydrocarbon-down, fluorocarbon-up configuration. (C) 1999 American Institute of Physics. [S0021-9606(99)71621-1].