Thermodynamics of aggregation of amphiphiles in solution from lattice Monte Carlo simulations

Monte Carlo simulations of a three-dimensional lattice model of an amphiphi le-solvent system are presented and examined for their usefulness in predic ting the thermodynamics of self-association of amphiphiles in solution, The size distribution of the aggregates obtained from the simulations is used- in combination with the mass action model-to obtain the thermodynamic prope rties of the solution of aggregates and to obtain expressions for the coeff icients of an empirical equation for the Gibbs energy available in the lite rature for aqueous nonionic surfactant solutions. The results are in good a greement with the empirical model, and the essential microstructural featur es and thermodynamic properties of the micellar solution can be extracted r easonably well using such an empirical fitting of the simulation data. The effects of the lengths of the solvophobic and solvophilic sections of the a mphiphile on critical micelle concentration extracted from the simulations are consistent with experimental results reported for several nonionic surf actants in water.