Novel sulfonated polyimides containing multiple cyano groups for polymer electrolyte membranes

Some multiple cyano groups functionalized sulfonated polyimides (CN-SPIs) are prepared derived from a novel CN-diamine monomer for the first time. Meanwhile, some similar SPIs but without cyano groups (Ph-SPIs) are prepared as counterparts for comparison purposes. Both chemical structure and properties of these SPIs are carefully characterized. At 100 degrees C, proton conductivities of some membranes could reach 0.138-0.146 S cm(-1), which are comparative with Nafion. The methanol diffusion coefficients of the membranes are between 1.74 and 5.82 x 10(-7) cm(2) s(-1), which are much more competitive than Nafion 117. It is of interest to find that cyano-functionalized SPIs could possess an excellent combination of low swelling, high proton conductivity and low methanol permeability. (C) 2013 Elsevier B.V. All rights reserved.