Enhancing Water Absorption in Sulfonated Poly(arylene ether sulfone) Polymer Electrolyte Membranes by Reducing Chain Entanglement through Constrained Deswelling

The water uptake of a polymer electrolyte membrane is a critical parameter that determines the dimensional stability and transport behavior in various energy conversion devices. In this study, the water uptake of a sulfonated poly(arylene ether sulfone) (SPAES) membrane was controlled solely by the number of chain entanglements without employing any water absorbents. Through the constrained deswelling process, the SPAES membrane achieved a significant enhancement in water uptake, increasing by up to 210% at room temperature. This notable improvement in water uptake originates from the reduction in elastic friction, represented by the number of chain entanglements, against the volume expansion resulting from the absorption of water by the sulfuric acid groups. Evidently, the controlled deswelling procedure led to biaxial stretching of the SPAES membrane, causing an increase in its surface area and a decrease in thickness. At the microscopic level, this controlled deswelling process might prompt the alignment of hydrophilic channels along the plane directions. These changes brought about by the controlled deswelling process resulted in changes to the membrane’s tensile characteristics and its transport behavior for protons and hydrogen gas.