Preparation and characterization of sulfonated polyetherimide/polyetherimide blend membranes

Polyetherimide (PEI) was sulfonated by chlorosulfonic acid (CSA) in 1,2-dichloroethane for the first time. With the increase of the CSA/PEI repeat unit ratio and/or reaction time, the ion-exchange capacity (IEC) of the sulfonated polyetherimide (SPEI) increased accordingly. Water-uptake testing and contact-angle measurement showed that the hydrophilicity of the SPEI increases with the increase of the IEC. Membranes were fabricated from SPEI/PEI blends with different ratios. The morphologies of the blend membranes were examined by scanning electron microscopy, which showed that the membrane pore size is larger when SPEI with higher IEC was used. With the increase of SPEI ratio in the blend membranes, the membrane pore size also increased. The contact-angle data of the membranes showed that the hydrophilicity of the blend membrane was elevated because of the sulfonate group on the SPEI molecular backbone. (C) 2004 Wiley Periodicals, Inc.