Amphiphilic aggregation in hydrogen bonding liquids: Dynamic and equilibrium properties

Abstract

In this work we study some dynamical and equilibrium properties of a lattice model for amphiphilic aggregation in the presence of van der Waals and associating solvents. The surfactant molecules are represented by flexible chains of connected sites on a cubic lattice, with a hydrophilic head and a hydrophobic tail. The hydrogen bonding solvent is similar to the square water in which each molecule occupies a single site, and can form hydrogen bonds with the nearest-neighbor solvent molecules if both have their bonds correctly aligned. By employing Monte Carlo simulations in the canonical ensemble, we obtained the aggregate-size distribution curve, the number of hydrogen bonds per molecule, and the residence time as well as the exit/entering rates of the amphiphiles from/to aggregates of different sizes. We compared the self-assembling properties in the presence of simple and structuring solvent by calculating the number of hydrogen bonds and the time correlations for the bulk and the first hydration shell of solvent molecules. We also studied the critical micellar concentration as a function of temperature for both kinds of solvents.