Chain architecture dependence of pore morphologies and water diffusion in grafted and block polymer electrolyte fuelcell membranes

Abstract

Using dissipative particle dynamics we model phase separation within block and grafted polymers composed of hydrophobic (A) and hydrophilic, acid-containing (C) beads. The grafted polymers have their hydrophilic beads located at the end of the grafted side chains. Pore morphologies are calculated at a hydration level λ of 4 H₂O molecules/C bead. Monte Carlo tracer diffusion calculations are used to model the restricted movement of water within the pore networks. For the block polymers we find that at fixed C bead fractions, or ion exchange capacity (IEC), an increase in C block length results in larger pores and increased water diffusion. For grafted polymers of equal IEC, increasing the side chain length results in a better connected pore network and increased long-range water mobility.