Dissipative Particle Dynamics Simulations on Mesoscopic Structures of Nafion and PVA/Nafion Blend Membranes

Abstract

Dissipative particle dynamics simulations were performed to study the mesoscopic structures of both humidified Nafion and polyvinyl alcohol(PVA)/Nafion blend membranes.Simulation results show that a phase-segregated microstructure is formed in both humidified Nafion and PVA/Nafion blend membranes.In humidified Nafion membrane,water molecules and sulfonate groups form tubular shaped water clusters.As the water content is increased,the size of water cluster is enlarged and water clusters percolate to form a continuous water channel.In the PVA/Nafion blend membrane,PVA,water molecules, and sulfonate groups together form hydrophilic domains.The mesoscopic structure of the PVA/Nafion blend membrane is affected by both the PVA/Nafion blend ratio and the water content in the membrane. When the PVA mass fraction is relatively low,PVA is predominantly distributed along the sulfonate groups of Nafion and as the PVA mass fraction is increased,PVA alone forms a distinct phase in the membrane. When the water content in the membrane is relatively low,water molecules are predominantly dissolved in PVA and as the water content is increased,spherical water clusters emerge in the membrane.This work provides further guidance for the development of PVA modified Nafion membranes for direct methanol fuel cell applications.