Coarse-grained study of the effect of hydrophobic side chain length on cluster size distributions and water diffusion in (amphiphilic-hydrophobic) multi-block co-polymer membranes

摘要: Abstract The formation of water clusters and their evolvement towards containing percolating networks at 16 vol% contents is studied by dissipative particle dynamics (DPD) for 7 multi-(amphiphilic-hydrophobic)-block co-polymer model membranes. amphiphilic (A[C]) block composed one hydrophobic A backbone bead to which a hydrophilic (acidic) side chain, represented C bead, attached. architecture the systematically varied contains x = 4 or 6 beads part Ax-p-q[Ap][Aq] family with chain lengths (p,q)= (0,0), (2,1), (3,0) (3,2), (4,1), (5,0) x = 6. Water diffusion derived from Monte Carlo trajectory simulations through 700 mapped morphologies reveal same trends as diffusivity during DPD simulations. For similar ion exchange capacity (or x) an increase in length difference, p-q, results better connected pores, cluster size, less isolated enhanced diffusion. These are explained assigning each polymer number Nbond bonds (DPD springs) between that nearest within polymer. (A-bead_Abead) contact matrices show high have propensity other beads. As result phase separation become more pronounced . Based on these findings alternative Nafion Dow membranes can be proposed large fraction ( CF2- CF2-) fragments distributed along chains.