New sulfonated engineering polymers via the metalation route. I. Sulfonated poly(ethersulfone) PSU Udel� via metalation-sulfination-oxidation

Abstract

A new process has been developed for the sulfonation of arylene polymers which can be lithiated, like polysulfone Udel®. The sulfonation process consists of the following steps: (1) lithiation of the polymer at temperatures from −50 to −80°C under argon, (2) gassing of the lithiated polymer with SO2; (3) oxidation of the formed polymeric sulfinate with H2O2, NaOCl, or KMnO4; (4) ion-exchange of the lithium salt of the sulfonic acid in aqueous HCl. The advantages of the presented sulfonation procedure are: (1) in principle all polymers which can be lithiated can be subjected to this sulfonation process; (2) by this sulfonation procedure the sulfonic acid group is inserted into the more hydrolysis-stable part of the molecule; (3) this process is ecologically less harmful than many common sulfonation procedures. The sulfonated polymers were characterized by NMR, titration and elemental analysis, by IR spectroscopy, and by determination of ionic conductivity. Also the hydrolytic stability of the sulfonated ion-exchange polymers was investigated. Polymers with an ion-exchange capacity of 0.5 to 3.2 mequiv SO3H/g Polymer have been synthesized and characterized. The following results have been achieved: membranes made from the sulfonated polymers show good conductivity, good permselectivity (>90%), and good hydrolytic stability in 1N HCl and water at temperatures up to 80°C. © 1996 John Wiley & Sons, Inc.