Dependence of pore morphology and diffusion on hydrophilic site distribution within hydrated amphiphilic multi block co-polymer membranes

Dissipative particle dynamics (DPD) combined with Monte Carlo (MC) tracer diffusion calculations are used to study phase separation and diffusion within hydrated (amphiphilic) alternating multi block co-polymer membranes. The co-polymers are composed of hydrophobic (A) and hydrophilic (C) fragments. The hydrophobic A block length is alternating short (x A fragments) and long (y A fragments). One repeat unit is represented as AxCAyC, with y ≥ x. The phase separated morphologies that were generated for 18 architectures by DPD at a water content of 25 percent by volume reveal that water is contained within a pore network with hydrophilic C fragments located near the pore boundary. The morphologies are mapped onto a cubic grid on which MC (tracer) trajectory calculations are performed in which particle movement is restricted to the water containing pore networks. For architectures for which the hydrophilic fragment fractions are the same (same ion exchange capacity), an increase in difference of hydrophobic block lengths (or y − x) result in a linear increase in inter pore distance and a significant increase in long-range diffusion through the pore networks.