Pore design within amphiphilic polymer membranes: linear versus Y-shaped side chain architectures

Abstract

Phase separation within polymer membranes is studied by Dissipative Particle Dynamics (DPD). The polymers are composed of hydrophobic backbone A beads to which side chains are attached. The side chains are linear or Y-shaped and contain a large fraction of A beads and one or two hydrophilic C beads. The Y shaped side chains contain 2C beads which are located at the end of each of the two branches whilst for the linear architectures the C beads are located at the end of each side chain. Phase separated morphologies are obtained at a water volume fraction of 16%. Water diffusion through the phase separated hydrophilic pore networks are deduced from (1) MC tracer diffusion calculations through selected frozen morphologies (in total 108 snapshots) and (2) from the water bead motions during the DPD simulations. Both methods reveal that the highest diffusion constants are obtained for the Y-shaped architectures. These results might be of importance to optimize the conductive pathways for proton diffusion in fuel cell membranes.