Dissipative particle dynamics simulation on the membrane formation of polymer-diluent system via thermally induced phase separation

Dissipative particle dynamics (DPD) simulations are carried out to study the structure and kinetics of membrane formation via thermally induced phase separation, taking into account the polypropylene-diphenyl ether (PP/DPE) system with neutral substrate on the mesoscale. According to the Flory-Huggins-DPD phase diagram, the interaction parameter between polymer and diluent in DPD is regulated to control the temperature. We investigate the effect of the deep and shallow quench on the membrane formation from early stage to late stage, including the corresponding membrane morphology. The results of the structure factor on the mesoscale indicate that the phase separation undergoes spinodal decomposition. Moreover, they are in accordance with the light scattering experiment results and the linear Cahn-Hilliard theory in the early stage. The domain size first reduces with time and then increases, which corresponds to that the number of the interfaces between polymer and diluent first increases, and then decreases to minimize the total free energy. In addition, our results show that the domain size has a more rapid growth in the intermediate stage. The information we gain from this study may benefit to understand the formation of membrane on the mesoscale. (C) 2010 Elsevier B.V. All rights reserved.