Mesoscopic simulation for the drying process of polymer films

A mesoscopic simulation method is presented to predict the drying behavior of polymer films using a dissipative particle dynamics method (DPD) with a simple model for evaporation. A gas phase is set above the polymer solution, and then evaporation of the solvent particle is calculated with appropriate parameters which lead solvent particles to prefer the gas phase rather than the polymer solution. A solvent particle that moves into the gas phase is considered as a gas particle after being determined as having evaporated. An effective mass is considered, so as to represent the relatively slower motion of the polymer particle compared to the solvent particle and the dependence of solvent diffusivity on its concentration in a polymer solution. A time-dependent profile of solvent concentration throughout the polymer film was successfully calculated, and skin formation, which indicates significant concentration gradients on the surface of the polymer film, was also observed.