Synthesis and characterization of proton‐conducting copolyimides bearing pendant sulfonic acid groups

Abstract

A series of sulfonated copolyimides (co‐SPIs) bearing pendant sulfonic acid groups were synthesized from 1,4,5,8‐naphthalenetetracarboxylic dianhydride (NTDA), bis(3‐sulfopropoxy) benzidines (BSPBs), and common nonsulfonated diamines via statistical or sequenced polycondensation reactions. Membranes were prepared by casting their m‐cresol solutions. The co‐SPI membrane had a microphase‐separated structure composed of hydrophilic and hydrophobic domains, but the connecting behavior of hydrophilic domains was different from that of the homo‐SPIs. The co‐SPI membranes displayed clear anisotropic membrane swelling in water with negligibly small dimensional changes in the plane direction of the membrane. With water uptake values of 39–94 wt %, they showed dimensional changes in membrane thickness of about 0.11–0.58, which were much lower than those of homo‐SPIs. The proton conductivity σ values of co‐SPI membranes with ion exchange capacity values ranging from 1.95–2.32 meq/g increased sigmoidally with increasing relative humidity. They displayed σ values of 0.05–0.16 S/cm at 50 °C in liquid water. Increasing temperature up to 120 °C resulted in further increase in proton conductivity. The co‐SPI membranes showed relatively good conductivity stability during the aging treatment in water at 100 °C for 300 h. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1545–1553, 2005

On the Development of Naphthalene-Based Sulfonated Polyimide Membranes for Fuel Cell Applications

“…We also synthesized side-chain-type SPIs bearing pendant sulfoalkoxy groups, such as 2,2 0 -bis(3-sulfopropoxy)benzidine (2,2 0 -BSPB) and 3,3 0 -bis(3-sulfo-propoxy)benzidine (3,3 0 -BSPB), of which the chemical structures are also shown in Figure 1, and investigated the water stability of their membranes. [32][33][34] The data are also summarized in Table I. The side-chaintype SPIs based on 2,2 0 -BSPB and 3,3 0 -BSPB displayed much better water stability than the mainchain-type SPIs.…”

“…For NTDA-2,2 0 -BSPB/BAPB (2/1)-s (M7) and NTDA-2,2 0 -BSPB/BAPPS (2/1) (M8), of which the sulfur losses were smaller, no appreciable change in ' was observed in the whole range of RH even after the aging for 300 h. On the other hand, for NTDA-2,2 0 (or 3,3 0 )-BSPB/BAPB (2/1) (M6-1 and M9-1), of which the sulfur losses were larger, the larger decrease in ' took place at the lower RHs, as in the case of the aging at 130 C. Thus, the BSPB-based SPI membranes displayed rather poor proton conductivity stability especially with the aging at 130 C. With the aging at 100 C, some membranes showed reasonably high proton conductivity stability. The BSPB-based SPI membranes have the microphase-separated structure, 34 and rather small difference in membrane morphology might play a large role on their proton conductivity stability.…”

“…As a result, a microphase separation structure composed of hydrophilic domains and hydrophobic moieties was well formed. 34 Because the hydrolysis of imide ring is an acid-catalytic reaction, if the protons are mostly restricted in the ion-rich domains isolated from the polymer main chain, the hydrolysis of imide ring of the SPI will be depressed. This is likely another reason for the excellent water stability of NTDA-BSPB.…”

Aromatic Poly(ether ketone)s with Pendant Sulfonic Acid Phenyl Groups Prepared by a Mild Sulfonation Method for Proton Exchange Membranes

“…29,30 Jannasch et al reported several side-group-acid poly-(ether sulfone)s with some attractive properties based on lithiation reaction. 24,31 Polyimides with side-group-acid substituents were also developed by Okamoto et al and Watanabe et al [32][33][34] To our knowledge, there are still no detailed reports related to the control of substitution sites through adjusting their various molecular structures. In addition, there are few reports of side-group-acid PEKs and their properties.…”

Sulphonated Biphenylated Poly(aryl ether ketone)s for Fuel Cell Applications

“…However, most of the scientific literature claiming to show good properties are only concerned with the PEM synthesis and basic membrane characterisation, while far less literature concerns work on membrane electrode assembly (MEA) and cell performance of hydrocarbon-based PEM materials [8].…”