Influence of Chemical Structure on Hydration and Gas Transport Mechanisms of Sulfonated Poly(aryl ether ketone) Membranes

Abstract

This work reports the influence of the chemical structure of two sulfonated poly(aryl ether ketone)s (SPAEK) on the hydration and gas transport mechanism of thin membranes made thereupon. For this purpose, two sulfonated poly(aryl ether ketone)s having the same ionic exchange capacity (IEC) but bearing a different repartition of the sulfonic acid groups along the polymer backbone were prepared. These polymers were synthesized by direct copolymerization of two specific sulfonated precursors, bisphenol AF and 4,4'-difluorobenzophenone. The morphology of the membranes was studied by transmission electron microscopy, and the thermal properties of the ionomers were determined from differential scanning calorimetry and thermogravimetric analyses. A detailed analysis of the water sorption isotherms and kinetics was performed. The gas transport properties were also determined for He, H(2), and CO(2) in the full range of water activity. From the detailed analysis of the water sorption isotherm and of the relative contributions of the Fickian diffusion and relaxation phenomena, a water sorption mechanism was proposed in relation with the SPAEK architectures and polymers' chain mobility. This mechanism allowed explaining the different evolution of the gas transport properties observed as a function of the gas nature and hydration rate.

Membrane reactors for the direct conversion of CO2 to dimethyl carbonate

“…This supports our observation that adding a layer of chitosan decreases the CO 2 permeability. The measured CO 2 permeabilities are in good agreement based on what could be expected for gas permeation through SPEEK membranes under humid conditions [8,40].…”

Polyaryletherketone in energy conversion and storage devices – a highly tailorable material with versatile properties

“…In all the range of water activity, the coexistence of both Fickian sorption behaviour and relaxation phenomenon was observed. Moreover, irrespective of diffused molecules (gas or water vapour), the solubility values were not affected by the presence of the sulfonic acid groups, while a significant effect was observed on the kinetic parameters 38 …”

Synthesis and investigation of sulfonated poly(p-phenylene)-based ionomers with precisely controlled ion exchange capacity for use as polymer electrolyte membranes

“…43,44 When dry, the S-PPBP domains are less permeable to gases than the PPBP domains due to their high cohesive energy density. 45 We could only obtain P O 2 values for S-PPBP-co-PPBP (1 : 1) under dry conditions; the amount of O 2 that permeated across the membranes of the other samples was too low to be detected with gas chromatography. Upon hydration, the humidity dependence of P H 2 of S-PPBP and S-PPBP-co-PPBPs rst presented concave forms with increasing humidity, and then increased linearly at >30% RH.…”

“…The second linear behavior under conditions of >30% RH might be caused by the plasticising phenomenon induced by water sorption. 45 When sulfonated membranes adsorb more water molecules, they begin to develop well-connected water clusters in hydrophilic domains, and these sorbed water molecules act to enhance the mobility of polymer chains, which results in increased gas permeation. Our results are in good agreement with these water sorption properties.…”