Percolation thresholds in hydrated amphiphilic polymer membranes

Water, proton, and oxygen transport in high IEC, short side chain PFSA ionomer membranes: consequences of a frustrated network

“…In the case of previous studies of ORR mass transport parameters determined for other polymer membranes containing more than 50 vol% water, including sulfonated, trifluorostyrenes, block copolymers, and various graft copolymers, under similar conditions, the measured diffusion coefficients and permeabilities are an order of magnitude greater, commensurate with their water content. 34,35 The observation that proton mobility, water permeance, and oxygen diffusion coefficient are all lower in value than anticipated leads us to the conclusions that hydrophilic percolation network for the transport of molecular species is much less developed in SSC membranes than it is for LSC membranes, as originally indicated by Kreuer et al, albeit for an alternate source of SSC PFSA ionomer membrane. …”

Morphology and diffusion within model membranes: Application of bond counting method to architectures with bimodal side chain length distributions

“…Also the selected v C 0 W = À2.6 is close to v C 0 W = À2.79 [30]. The motivation to select these v-values (Table 2) is that well phase separated morphologies are obtained [34,[40][41][42][43][44]53] and allows to compare the results with an already developed database for this set of v parameters.…”

“…Usually the volumes V represented by each type of DPD bead are chosen to be the same. In modeling fuel cell membranes they are typically in between V = 0.06 nm 3 [34,39,41,42] and V = 0.18 nm 3 [35,36]. These correspond to the volume occupied by N m = 2 and N m = 6 water molecules, respectively.…”

“…a bimodal distribution of C beads within the backbone), pore size and water diffusion increases with bimodal character (or asymmetry parameter y/x) [40]. For grafted polymers for which the side chains are distributed equidistantly along the polymer backbone (uni-modal distribution) and with a single pendent hydrophilic fragment, the size of the water containing pores and water diffusion coefficients increase with side chain length [41]. When the side chains are kept at the same length but the inter-branching distance along the backbone is alternatingly long and short (y > x, bimodal distribution), the pore size and diffusion increases with increase of bimodal character, or asymmetry parameter y/x [34,42,43].…”

“…For example, at hydration level of k = 5 water molecules per SO 3 H site, Pivovar and Pivovar [37] measured a local water mobility of $1.6 Â 10 À5 cm 2 /s, which is $70% of the pure water value of 2.3 Â 10 À5 cm 2 /s. In later works [34,[39][40][41][42][43][44] where DPD was applied in combination with MC tracer diffusion calculations it was found/predicted that among membranes of the same IEC the pore morphology and diffusion constants depend strongly on the specific architecture of the model polymers. The main obtained trends are summarized below.…”