Understanding structure and transport characteristics in hydrated sulfonated poly(ether ether ketone)?sulfonated poly(ether sulfone) blend membranes using molecular dynamics simulations
JMS 429 (2013) 384?395
Chen Song and Ben Corry
 Department of Chemical Engineering, Amirkabir University of Technology, Tehran, Iran
 Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran, Iran
Using molecular dynamics, polymeric acid-acid blend membranes were studied at varied water contents sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(ether sulfone) (SPES).
Simulation components were SPEEK and SPES polymeric chains, hydronium ions, and water molecules. SPEEK and SPES were constructed from their corresponding monomers using the Polymer Builder module of Materials Studio software and were made to undergo a degree of polymerization of 20. The DREIDING force field was used to build the polymeric chains. F3C model was used for water while the parameters from Jang et al were used for the hydronium ions. All MD simulations were done in LAMMPS.
In order to analyze the static/structural properties of the acid blended membranes, radial distribution functions (RDFs) and coordination numbers of the sulfonic acid groups, the oxygen atoms of water molecules, and the hydronium ions were obtained. Results show that the equilibrated structure of the SPEEK-SPES blend membrane experiences hydrophobic-hydrophilic phase separation and swelling when solvated by water. Clustering of water molecules with and hydronium ions were also observed, but the extent of phase separation in the studied acid blend membranes was less pronounced than that in a hydrated Nafion membrane. The transport properties of the membranes were also investigated by analyzing the mean squared displacement (MSD) of hydronium ions and water molecules. From the MSD value, diffusivity of the membrane was calculated using the Einstein relation.
Contribution and application:
This paper has provided a detailed methodology of creating polymeric membrane models for MD simulations. The authors have provided which software they used and the forcefields they used. The paper reviewed could be useful for our lab as we study polymeric RO membranes.
By: Hannah Ebro