Phase diagram for the lattice model of amphiphile and solvent mixtures by Monte Carlo simulation

Abstract

Results are presented from a Metropolis Monte Carlo simulation in the NVT ensemble of a three-dimensional lattice model of an amphiphile and solvent mixture. In this model the amphiphiles are represented as flexible chains of adjacent sites with one site at the end of the chain representing the solvophobic head site.

The simulation exhibits self-assembly of micelles, vesicles and bilayers from random starting configurations. A temperature–concentration phase diagram is obtained for chains of length four with a fixed value of head–solvent interaction. At low concentrations the model exhibits a sharp critical micelle concentration despite a high cluster size polydispersity and a weak minimum in the cluster size distribution. The micelles grow with increasing concentration and form cylindrical structures. At high concentrations the system exhibits a transition from a bicontinuous phase at high temperatures to a lamellar phase at low temperatures.