Modification of SPPESK proton exchange membranes through layer-by-layer self-assembly

Abstract

Sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) composite membranes are fabricated through electrostatic layer-by-layer (LbL) self-assembly method with chitosan (CS) and phosphotungstic acid (PWA) to enhance the proton conductivity and stability. The results demonstrate that LbL self-assembly has different effects on the SPPESK membrane substrates with different sulfonation degrees (DSs). It elevates proton conductivity of the SPPESK membrane of lower DS and enhances swelling stability of the SPPESK membrane of higher DS. For instance, at 80°C, proton conductivity of the SPPESK0.74/(CS/PWA) 1 membrane (lower DS) increases by 16%-96.49 mS cm -1, and swelling ratio of the SPPESK1.01/(CS/PWA) 3 membrane (higher DS) decreases from 58 to 29%. Attribute to the electrostatic interaction and ion cross-linking networks, permeability of the SPPESK0.74/(CS/PWA) 3 membrane and the SPPESK1.01/(CS/PWA) 5 membrane are reduced by 45 and 30%, respectively. The results indicate that the LbL self-assembly has broadened the available DS range for fuel cell applications.