Dissipative Particle Dynamics Simulation for Clarifying Mechanism of Water Permeation in Polymeric Membranes

Abstract

Polymeric membranes are widely used in engineering fields such as fuel cells and heat storage materials. The polymeric membrane has two properties, which are selective permeability and barrier. The selective permeation mean to let only certain substances pass through porimeric membrane. For example, it is used for fuel cells. The polymeric membrane used in fuel cells allow protons to pass through, but does not water and oxygen. Next, barrier is to not permeate anything. This is used for a microcapsule of a heat storage material and so on. The microcapsule is made of polymers and designed as substances in capsules are not discharged from it. In future, It will be used as CO2 separation technology or seawater desalination, which will be anticipated to solve global issues. However, the prediction and control of penetration into a membrane are still challenging subjects. In this research, we aimed to elucidate the mechanism of the water permeation. because water permeation is most basic. We performed molecular simulations of water transport through a polymeric membrane to clarify the key factors that dominate water permeation. We employed the dissipative particle dynamics (DPD) method. DPD method is a powerful mesoscopic simulation tool which enables the simulation of events occurring in millisecond timescales and on micrometre length scales. Since its introduction a decade ago, this method has been used to model various membrane cell systems, including the self-assembly of amphiphilic molecules interaction with rigid nanoparticles, and the effect of ligands and receptors in the membrane. Therefore, this method is suitable to simulate polymeric membrane system. we used model of actual molecules (COP (membrane polymer), sodium acetate (additive) and water). To determine the interaction parameters of the simulation models, we used the J-OCTA simulation software. We first computed the time-averaged mean square displacement (MSD) of water molecules to evaluate water permeability into a polymeric membrane. Then, MSD was also calculated for the additive system. Comparing of the systems, it was found that the water permeability decrease by adding additives (figure). The results were also reproduced in experiments and we get qualitatively same results. We found that additives enable the reduction of the water permeability into a polymeric membrane. In addition, we discussed polymer synthesis guideline decreasing water permeability. Figure 1