4,4/-Diaminodiphenyl ether-2,2 -disulfonic

Fang, J., Guo, X., Harada, S., Watari, T, Tanaka, K., Kita, H., and Okamoto, K., 2002, Novel sulfonated polyimides as polyelectrolytes for fuel cell application. 1. Synthesis, proton conductivity, and water stability of polyimides from 4,4 -diaminodiphenyl ether-2,2 -disulfonic acid. Macromolecules 35 9022-9028. 

Most main-chain sulfonated diamines are synthesized by direct sulfonation of a non-sulfonated precursor (Pig. 6) or its dinitro analogue [69]. 4,4 -Diaminodiphenyl ether-2,2 -disulfonic acid (ODADS), 4,4 -bis(4-aminophen-oxy)biphenyl-3,3 -disulfonic acid (BAPBDS) [71,72], 2,2 -bis[4-(4-amino-phenoxy)hexafluoroisopropane disulfonic acid (BAHFDS) [73,74], 9,9-bis (4-aminophenyl)fluorene-2,7-disulfonic acid (BAPFDS) [35], and 2,2 -bis(4-aminophenoxy)biphenyl-5,5 -disulfonic acid (o-BAPBDS) [75] were synthesized accordingly. Because of the electrophihc nature of the sulfonation reaction, the sulfonic acid groups are usually introduced in the ortho/para position to the electron-donating substituents. Polymer-grade monomers are obtained with excellent yields (83, 85, and 90%, respectively, for BAPFDS, ODADS, and p-BAPBDS), except in some cases (o-BAPBDS, 48%). 

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