Hydrocarbon-based composite membranes containing sulfonated Poly(arylene thioether sulfone)-grafted 2D crown ether framework coordinated with cerium ions for PEMFC applications

We propose a novel strategy to develop sulfonated poly(arylene ether sulfone) (SPAES) composite membranes that can simultaneously improve the physicochemical stability and proton conductivity of hydrocarbon-based membranes for PEMFC applications. This strategy involves the use of a sulfonated poly(arylene thioether sulfone)-grafted 2D crown ether framework coordinated with cerium³⁺ ions (SATS–C₂O–Ce) as a promising filler material. SATS-C₂O, a highly sulfonated polymer-grafted 2D framework containing crown ether holes in its skeletal structure, was prepared via self-condensation using halogenated phloroglucinol as a multifunctional building unit to form C₂O, followed by condensation using SATS to graft the sulfonated polymer onto its edge. Ce³⁺ ions were directly coordinated within the crown ether holes of SATS-C₂O via a simple doping process using aqueous Ce solution. The SPAES composite membranes containing SATS–C₂O–Ce (SPAES/SATS–C₂O–Ce) exhibited exceptional dimensional stability and mechanical toughness. The remarkable chemical stability of SPAES/SATS–C₂O–Ce compared to that of pristine SPAES and SPAES/Ce (containing the same amount of Ce³⁺ ions but without SATS-C₂O) was attributed to the well-dispersed state of Ce³⁺ ions within the SPAES matrix. Furthermore, the enhanced proton conductivity of SPAES/SATS–C₂O–Ce surpassed those of pristine SPAES, SPAES/C₂O, and SPAES/Ce by the formation of additional proton-conducting channels provided by the sulfonic acid groups of SATS–C₂O–Ce, along with the improved water uptake capability of SPAES.