Phase Separation and Water Channel Formation in Sulfonated Block Copolyimide

Abstract

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Sulfonated hydrocarbon membranes for medium-temperature and low-humidity proton exchange membrane fuel cells (PEMFCs)

“…Despite the low ion exchange capacity (e.g., IEC of Nafion ® 112 = 0.9 mequiv. g −1 ), Nafion ® PFSA membranes have a high acidity due to the electron-withdrawing characteristics of fluorine atoms around the terminal sulfonic acid groups on the side chains [16,[35][36][37][38]. PFSA membranes also form water channels effectively, despite the low water uptake, as a result of the strong phase separation between extremely hydrophobic backbones and hydrophilic side chains ( Fig.…”

“…PFSA membranes also form water channels effectively, despite the low water uptake, as a result of the strong phase separation between extremely hydrophobic backbones and hydrophilic side chains ( Fig. 2(a)) [12,16,[38][39][40]. In particular, the flexibility of the acidic side chains allows the ready formation of water channel [38].…”

“…2(a)) [12,16,[38][39][40]. In particular, the flexibility of the acidic side chains allows the ready formation of water channel [38]. Consequently, PFSA membranes display high proton conductivity and dimensional stability [16,38,39,41].…”

“…In particular, the flexibility of the acidic side chains allows the ready formation of water channel [38]. Consequently, PFSA membranes display high proton conductivity and dimensional stability [16,38,39,41]. However, a number of issues such as cost, safety, the dehydration and consequent loss of conductivity at elevated temperature hinder the widespread commercialization of PEMFCs that use PFSA membranes.…”

“…2(b)) [12,16,[38][39][40]. Consequently, sulfonated hydrocarbon PEMs exhibit relatively low proton conductivities even at high ion exchange capacities (IECs) and excessive swelling behavior under hydrated conditions (i.e., low dimensional stability) [16,38].…”