Simulation of the Phase Behavior of the (EO)13(PO)30(EO)13(Pluronic L64)/Water/p-Xylene System Using MesoDyn

Abstract

The phase behavior of the (EO)13(PO)30(EO)13(Pluronic L64)/water/p-xylene system in the mesoscopic region was investigated using MesoDyn, a new dynamic density functional method. The “equivalent chain” method was used to perform the parametrization of the Gaussian chain. In this paper, we compare the mesoscopic morphology formations of systems at different concentrations of solvents and discuss the effect of water on the formation of micelles. The calculated results show that Pluronic L64 does not form polymolecular micelles in pure p-xylene or in the presence of a small amount of water, but with an increase in the concentration of water, polymolecular micelles in different shapes were formed. By analyzing the water distributions of the systems after 1000 simulation steps, we prove that free water does exist in the micellar core. The effects of temperature and PEO and PPO block sizes are also investigated. The results indicate that the formation of reverse micelles is exothermic, and so the formation of reverse micelles becomes more difficult and the rate becomes slower with increasing temperature. Moreover, PEO block size has a stronger effect on the formation of reverse micelles compared with that of the PPO block size. In the microscopic region, phase behavior can be modeled using a detailed molecular description, often with techniques such as molecular dynamics (MD) and Monte Carlo (MC) simulations. In the macroscopic region, phase separation models can be based on equations of state, which are fitted to macroscopic phase diagrams. In the mesoscopic region, local concentration fields can be used as collective variables to obtain a description of self-assembly structures. The mesoscopic dynamics models are receiving increasing attention as they form