Assessing the Influence of Side-Chain and Main-Chain Aromatic Benzyltrimethyl Ammonium on Anion Exchange Membranes

Abstract

3,3'-Di(4″-methyl-phenyl)-4,4'-difluorodiphenyl sulfone (DMPDFPS), a new monomer with two pendent benzyl groups, was easily prepared by Suzuki coupling reaction in high yield. A series of side-chain type ionomers (PAES-Qs) containing pendant side-chain benzyltrimethylammonium groups, which linked to the backbone by alkaline resisting conjugated C-C bonds, were synthesized via polycondensation, bromination, followed by quaternization and alkalization. To assess the influence of side-chain and main-chain aromatic benzyltrimethylammonium on anion exchange membranes (AEMs), the main-chain type ionomers (MPAES-Qs) with the same backbone were synthesized following the similar procedure. GPC and (1)H NMR results indicate that the bromination shows no reaction selectivity of polymer configurations and ionizations of the side-chain type polymers display higher conversions than that of the main-chain type ones do. These two kinds of AEMs were evaluated in terms of ion exchange capacity (IEC), water uptake, swelling ratio, λ, volumetric ion exchange capacity (IECVwet), hydroxide conductivity, mechanical and thermal properties, and chemical stability, respectively. The side-chain type structure endows AEMs with lower water uptake, swelling ratio and λ, higher IECVwet, much higher hydroxide conductivity, more robust dimensional stability, mechanical and thermal properties, and higher stability in hot alkaline solution. The side-chain type cationic groups containing molecular configurations have the distinction of being practical AEMs and membrane electrode assemblies of AEMFCs.

Polybenzimidazole-crosslinked poly(vinylbenzyl chloride) with quaternary 1,4-diazabicyclo (2.2.2) octane groups as high-performance anion exchange membrane for fuel cells

“…6a). The calculated E a for PBI-c-PVBC/OH was 5.5 kJ mol À1 , which is smaller than that of AEM usually reported in the literature (8e30 kJ mol À1 ) [13,46e49], indicating the low resistance of OH À transport in the membrane probably due to the side-chain-type ionic transport group (quaternized DABCO) and conductive main-chain backbone (conductive crosslinking point in PBI) [46,48]. Despite of such high hydroxide conductivity, the swelling degree and water uptake of PBI-c-PVBC/OH was only~13% and~67%, respectively, and they nearly did not grow with the increase of temperature (Fig.…”

Alkali resistant cross-linked poly(arylene ether sulfone)s membranes containing aromatic side-chain quaternary ammonium groups

“…Poly(arylene ether sulfone) containing benzylmethyl sidechains (PAES-Me) and bromomethylated poly(arylene ether sulfone)s (PAES-Brs) were synthesized according to the previously reported methods [30]. GPC result of PAES-Me: M n ¼107 kg mol À 1 , M w ¼214 kg mol À 1 , M w /M n ¼2.0.…”

“…[10] MPAES-Q-2, 11.46 kJ mol À 1 [30]). By contrast, the ion transport activation energies of the cross-linked CPAES-Qs AEMs vary from 9.9 to 10.7 kJ mol À 1 .…”

“…In this work, we construct a series of AEMs having a combination of the cross-linked structures and the end benzyltrimethyl ammonium groups of aromatic side-chain with commercial available 4,4 0 -dihydroxyldiphenyl and a newly reported difluorodiphenyl sulfone monomer of our group, which has two pendent benzyl groups and is synthesized by Suzuki coupling [30]. The IEC m values of the cross-linked AEMs were well controlled by adjusting the brominations and the heating cross-linking reactions of the precursors.…”

Densely quaternized anion exchange membranes synthesized from Ullmann coupling extension of ionic segments for vanadium redox flow batteries

“…[4]. These AEMs are usually flexible and robust, with tunable ion exchange capacities (IECs), water uptakes, and anion conductivities [25,26].…”