Monte Carlo Simulation of the Formation of Layered Structures and Membranes by Amphiphiles

(Received 22 March 1995, accepted 28 March 1995)

Abstract
We investigate a Larson-type model of a ternary mixture of nonionic amphiphiles, water and oil confined between walls or forming a membrane by performing Monte Carlo simulations on a cubic lattice. We compute the concentration profiles of water/oil and the distribution of the amphiphiles with varying temperatures and distance from a solid wall. For temperatures below the critical temperature for demixing of oil-water and amphiphiles on cubic lattices, we observe an oscillatory pattern in the distribution of the water/oil molecules. We also examine the stability of membranes both in an extended system and when confined between walls. Below the critical demixing temperature, double layer membranes are stable when there is no oil present. We find that single layers are stable only when between walls and if we start with a finite amphiphile concentration away from the membrane. At higher temperatures, we also observe the development of periodic layered structures for one type of amphiphile.