Synthesis and characterization of benzimidazolium-functionalized polysulfones as anion-exchange membranes

Abstract

Anion‐exchange membranes containing pendant benzimidazolium groups were synthesized from polysulfone by chrolomethylation followed by nucleophilic substitution reaction with 1‐methylbenzimidazole. The structures of the polymers were characterized by 1H‐NMR and FTIR analysis. The resulting membranes showed high thermal stability below 200 °C. The values of water uptake and swelling degree increased with the ion‐exchange capacity of the polymeric membrane. The ionic conductivity was measured by means of impedance spectroscopy in aqueous solution of potassium hydroxide (10−4−10−1 M). The results show not only a clear correlation between the membrane's electrochemical behavior with the electrolyte solution embedded in the membrane, but also with the degree of the polysulfone's chloromethylation.Thus, the ionic conductivity increased more than two orders of magnitude when the degree of chloromethylation increased from 40 to 140%. Benzimidazolium‐functionalized polysulfones exhibited better thermal, mechanical, and electrochemical properties than the widely used polymeric membranes containing quaternary ammonium groups. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2363–2373

DABCO-functionalized polysulfones as anion-exchange membranes for fuel cell applications: Effect of crosslinking

“…The chloromethylation reaction of PSU was carried out as described by Pérez‐Prior et al First, PSU (5.00 g) was dissolved in chloroform (250 mL) with mechanical stirring in a three‐neck round bottom flask. After adding stannic chloride (0.27 mL) and paraformaldehyde (6.79 g) to the solution of PSU, chlorotrimethylsilane (28.64 mL) was added dropwise.…”

“…AEMs are formed by a polymeric backbone functionalized with fixed cationic groups as  ,  , or  and hydroxide ions which act as counter anions that sustain the conductivity . Polymers such as poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO), poly(vinyl alcohol) (PVA), polybenzimidazole (PBI), poly(arylene ether sulfone) (PES), or polysulfone (PSU) are widely used for this purpose. In addition, complex mixtures of polymers were also prepared to improve the properties of the resulting membranes.…”

“…Furthermore, this polymer presents two activated positions per repeat unit towards electrophilic aromatic substitution leading to high degrees of functionalization. Among the functional groups used to prepare conducting polymers stand out the trimethyl ammonium (TMA), imidazolium (Im), benzimidazolium (BIm), guanidinium (Gua), or DABCO groups. However, in the case of DABCO, the presence of two nitrogen atoms in this structure makes this group susceptible to be tethered through two positions favoring thus the crosslinking effect besides of acting as quaternized agent .…”

Comb-shaped guanidinium functionalized poly(ether sulfone)s for anion exchange membranes: Effects of the spacer types and lengths

“…Therefore, over the past decade, many kinds of cations, including quaternary ammonium (QA), imidazolium, guanidinium, phosphonium, sulfonium, 1,2,3‐triazolium, and metal‐based cations, have been explored and utilized in polymer electrolytes. Possibly due to the fabrication simplicity, these cationic moieties mainly located on the benzylic site of polymer backbone, such as polystyrene, poly(ether sulfone) (PES) and poly(phenylene oxide) (PPO), to the construction of AEM.…”

“…4,5 As a solid polymer electrolyte, anion exchange membrane (AEM) is a key component in AEMFCs, acting as the role of hydroxide conduction, fuel, and oxidant stream separation. 6,7 Therefore, over the past decade, many kinds of cations, including quaternary ammonium (QA), [8][9][10][11][12][13][14][15][16][17][18] imidazolium, [19][20][21][22][23][24] guanidinium, [25][26][27][28] phosphonium, 29,30 sulfonium, 31,32 1,2,3-triazolium, 33 and metal-based cations, 34,35 have been explored and utilized in polymer electrolytes. Possibly due to the fabrication simplicity, these cationic moieties mainly located on the benzylic site of polymer backbone, such as polystyrene, poly(ether sulfone) (PES) and poly(phenylene oxide) (PPO), to the construction of AEM.…”