Structure and Properties of Cation Exchange Membrane made of Sulfonated Polyethersulfone

In this work a new process was developed for the sulfonation of the chemicallly stable engineering polymer polyethersulfone as membrane materials for electrodialysis or a flow battery applications. Commercially available polyethersulfone polymer was partially sulfonated using a CSA sulfonating agent in a dichloromethane solvent, which sulfonated polyethersulfone with various sulfonation levels have been prepared. Sulfonated polyethersulfone (SPES) membranes with different ion capacities were prepared for the purpose of identifying cation exchange membrane properties, in an attempt to find a low cost replacement for Nafion, which most of the perfluorinated membranes, known to exhibit a prolonged service life, are expensive and difficult to process. The following features were determined: the degree of sulfonation, water uptake, thermal analysis, and electrochemical properties such as ion exchange capacities, resistivity, selectivity of ion permeation. The surface of the cation exchange membranes, decomposed with the H202-treatment, were observed by using scanning electron microscope. The area resistivities of SPES mebranes in 5N-NaOH decreased from $2,150{\;}{\Omega}-cm2$ to less than $15{\Omega}-cm2$ as the ion exchange capacity (IEC) increased from 0.62 to 1.73 millieequivlants per dry gram(meq/dg).eq/dg).