MOLECULAR-DYNAMICS SIMULATION OF DOMAIN FORMATION IN LANGMNIR MONOLAYERS OF MOLECULES WITH DIPOLE-MOMENTS

A two-dimensional molecular dynamics model of dimers and monomers with in-plane and off-plane dipole moments is set up in order to test the importance of different anisotropic forces on the creations of pinned labyrinthine-like domains, observed in monolayers. The model is design ed especially in such a way as to simulate the domain growth in Langmu ir monolayers of diglycerides or phospholipids. The simulations show t hat in-plane dipole moments only have a minor impact on the domain gro wth, whereas the off-plane dipole moments inhibit the domain formation . The dimers align for big values of the off-plane dipole moment and m aintain in a pinned, non-equilibrium conformation. For smaller values of the off-plane dipole moments the mean size of the phases grow algeb raically, R(t) = at(n); but slower than in the case of no dipole momen t. This behaviour is explained by that the created interfaces constitu te a strong and repulsive field which slows down the phase separation.