Sulfonated polyimides containing triphenylphosphine oxide for proton exchange membranes

A series of sulfonated co-polyimides (co-SPI) were prepared by one pot polycondensation reaction of a combination of diamines namely; 4,4'-diaminostilbene-2,2'-disulfonic acid (DSDSA) and prepared nonsulfonated diamine (DATPPO) containing triphenylphosphine oxide with 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA). All these soluble co-SPI gave flexible membranes with high thermal stability and showed good mechanical property. Transmission electron microscopy (TEM) analysis revealed the microphase separated morphology with well-dispersed hydrophilic (cluster size in the range of 5-55 nm) domains. The co-SPI membranes showed high oxidative and hydrolytic stability with higher proton conductivity. All these co-SPI membranes exhibited low water uptake and swelling ratio. The co-SPI membrane TPPO-60 (60% degree of sulfonation) with IECW = 1.84 mequiv g(-1) showed high proton conductivity (99 mS cm(-1) at 80 degrees C and 107 mS cm(-1) at 90 degrees C) in water with high oxidative (20 h) and hydrolytic stability (only 5% degradation in 24 h). (C) 2016 Elsevier B.V. All rights reserved.