Activity coefficient of monomer in different aggregates of a surfactant solution: a Lattice Monte Carlo Study

In this paper, canonical lattice Monte Carlo simulation technique is used to derive cluster size distribution of a surfactant solution, by which activity coefficient of a monomer in solution and in the micellar phase is estimated. To do this, correlation of cluster concentration with the aggregation number is needed. The multiple equilibrium method is used to relate cluster size distribution to the activity coefficient. The introduced idea is not only applicable to the lattice model techniques, but also to any method that can produce cluster size distribution. The method can be used as a reference to test activity coefficient data of lattice-based equations of state. Results show that the activity coefficients of monomers in micellar aggregates are much greater than unity, in accordance with the experimental results.