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A series of cross‐linked AEMs (c‐DQPPO/PVA) are synthesized by using rigid polyphenylene oxide and flexible poly(vinyl alcohol) as the backbones. Dual cations are grafted on the PPO backbone to improve the ion exchange capacity (IEC), while glutaraldehyde is introduced to enhance compatibility and reduce swelling ratio of AEMs. In addition to the enhanced mechanical properties resulting from the rigid‐flexible cross‐linked network, c‐DQPPO/PVA AEMs also exhibit impressive ionic conductivity, which can be attributed to their high IEC, good hydrophilicity of PVA, and well‐defined micro‐morphology. Additionally, due to confined dimension behavior and ordered micro‐morphology, c‐DQPPO/PVA AEMs demonstrate excellent chemical stability. Specifically, c‐DQPPO/PVA‐7.5 exhibits a wet‐state tensile strength of 12.5 MPa and an elongation at break of 53.0 % at 25 °C. Its OH− conductivity and swelling degree at 80 °C are measured to be 125.7 mS cm−1 and 8.2 %, respectively, with an IEC of 3.05 mmol g−1. After 30 days in a 1 M NaOH solution at 80 °C, c‐DQPPO/PVA‐7.5 experiences degradation rates of 12.8 % for tensile strength, 27.4 % for elongation at break, 14.7 % for IEC, and 19.2 % for ion conductivity. With its excellent properties, c‐DQPPO/PVA‐7.5 exhibits a peak power density of 0.751 W cm−2 at 60 °C in an H2‐O2 fuel cell. [ABSTRACT FROM AUTHOR]

The rise of heterocycle cations, a new class of stable cations, has fueled faster growth of research interest in heterocycle cation‐attached anion exchange membranes (AEMs). However, once cations are grafted onto backbones, the effect of backbones on properties of AEMs must also be taken into account. In order to comprehensively study the influence of cations effect and backbones effect on AEMs performance, a series of AEMs were prepared by grafting spacer cations, heterocycles cations, and aromatic cations onto brominated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (BPPO) or poly(vinylbenzyl chloride) (PVB) backbones, respectively. Spacer cation [trimethylamine (TMA), N,N‐dimethylethylamine (DMEA)]‐attached AEMs showed general ion transportation and stability behaviors, but exhibited high cationic reaction efficiency. Heterocycle cation [1‐methylpyrrolidine (MPY), 1‐methylpiperidine (MPrD)]‐attached AEMs showed excellent chemical stability, but their ion conduction properties were unimpressive. Aromatic cation [1‐methylimidazole (MeIm), N,N‐dimethylaniline (DMAni)]‐attached AEMs exhibited superior ionic conductivity, while their poor cations stabilities hindered the application of the membranes. Besides, it was found that PVB‐based AEMs had excellent backbone stability, but BPPO‐based AEMs exhibited higher OH− conductivity and cation stability than those of the same cations grafted PVB‐based AEMs due to their higher water uptake (WU). For example, the ionic conductivities (ICs) of BPPO‐TMA and PVB‐TMA at 80 °C were 53.1 and 38.3 mS cm−1, and their WU was 152.3 and 95.1 %, respectively. After the stability test, the IC losses of BPPO‐TMA and PVB‐TMA were 21.4 and 32.2 %, respectively. The result demonstrated that the conductivity and stability properties of the AEMs could be enhanced by increasing the WU of the membranes. These findings allowed the matching of cations to the appropriate backbones and reasonable modification of the AEM structure. In addition, these results helped to fundamentally understand the influence of cation effect and backbone effect on AEM performance. [ABSTRACT FROM AUTHOR]

Preparing AEMs with robust mechanical properties, high ionic conductivity and excellent chemical stability is challenging. Here, cross-linked/aggregated AEMs are prepared by incorporating hydrophilic Jeffamine cross-linkers and hydrophobic side chains into the rigid quaternized poly (vinyl benzyl chloride). Jeffamine's flexibility ensures high elongation at break of the cross-linked/aggregated membranes (125.0–199.8%). The hydrophobic side chain limits excessive water absorption and facilitates self-aggregation of hydrophilic and hydrophobic domains, enhancing tensile strength (5.08–7.40 Mpa in wet state) and improving ionic conductivity of the AEMs (73.8–110.4 mS cm−1 at 80 °C). Alkali-resistant PVB, restricted dimensionality, and ordered micro-phase separation morphology contribute to outstanding chemical stability of the AEMs. Degradation of both backbones and cations is <20% after treatment in 1 M NaOH solution at 80 °C for 30 days. Based on the membrane, a peak power density of 354.4 mW cm−2 at 60 °C is yielded. PVB based AEMs of c (Je) a Cx-QAPVB exhibit excellent flexibility, outstanding alkali-resistant and high hydroxide ion conductivity. [Display omitted] • Highly flexible and transparent poly (vinyl benzyl chloride) based anion exchange membranes are prepared. • Anion exchange membranes exhibit improved ionic conductivity and robust stability. • A peak power density of 354.4 mW cm−2 is presented. [ABSTRACT FROM AUTHOR]

Balancing ion conductivity, mechanical strength, and alkali stability is a significant challenge in the application of anion exchange membranes (AEMs) in anion exchange membrane fuel cells (AEMFCs). In this study, rigid poly(4-vinylbiphenyl chloride) (PVB) and flexible polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) are selected as the polymer backbones to create semi-interpenetrating network (SIPN) AEMs. To achieve high ionic conductivity, quaternary ammonium groups are grafted onto each PVB structural unit, and TMHDA reacts with CMSEBS to construct a cross-linking network while also generating quaternary ammonium groups. This approach, along with well-defined micro-morphology, result in SIPN-SEBS/PVB-10 exhibiting an impressive ionic conductivity of 105.7 mS cm−1 at 80 °C. The SIPN structure, formed by the linear quaternary ammonium PVB and cross-linked SEBS, enhances the compatibility between the rigid and flexible components, resulting in good tensile strength (>14.5 Mpa) and elongation at break (>31.8%) for SIPN-SEBS/PVB AEMs at 25 °C in the wet state. Furthermore, SIPN-SEBS/PVB AEMs exhibit excellent chemical stability, in addition to the restricted swelling behavior, which can be attributed to the stable PVB and SEBS main chains. After immersion in a 1 M NaOH solution at 80 °C for 30 days, the degradation of backbones and cations in all membranes is less than 10% and 20%, respectively. Moreover, the peak power density of SIPN-SEBS/PVB-10 in an H 2 /O 2 single fuel cell reaches an impressive value of 379 mW cm−2. Based on these excellent properties, the developed SIPN AEMs hold great promise as candidates for AEMFCs. Structure diagram and photos of SIPN-SEBS/PVB AEMs. And the single fuel cell performance by using SIPN-SEBS/PVB-10 as the separator. [Display omitted] • A new perspective is offered on the development of AEMs with high performance. • Semi-interpenetrating network AEMs is achieved using linear QPVB and cross-linked c QSEBS. • A peak power density of 379 mW cm−2 is presented. [ABSTRACT FROM AUTHOR]

A series of highly transparent semi-interpenetrating polymer network anion exchange membranes (SIPN AEMs) composed of a flexible and cation cross-linked polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (c QSEBS) component, and a rigid, highly-charged quaternized poly(2,6-dimethyl phenylene oxide) (QPPO) component are prepared. Flexible and rigid polymer backbones endow SIPN AEMs with excellent flexibility and mechanical strength. High charge content and well defined hydrophilic/hydrophobic phase separation patterns ensure SIPN AEMs with improved ionic conductivity. Alkali-resistant SEBS, enhanced dimensional stability and ordered microphase separation morphology contribute to the good chemical stability of SIPN-AEMs. Among these AEMs, SIPN- c QSEBS/QPPO-10 with an IEC of 1.93 mmol g−1 achieves a better trade-off between tensile strength (19.36 MPa at 25 °C in wet state), flexibility (58.43% at 25 °C in wet state) and OH− conductivity (103.1 mS cm−1 at 80 °C). Besides, SIPN- c QSEBS/QPPO-10 shows low swelling degree (15.4% at 80 °C) and high chemical stability (95.9%, 88.7%, 82.7% and 88.5% retention in weight, OH− conductivity, tensile strength and elongation at break, respectively, after immersing in 1 M NaOH at 80 °C for 30 days). Importantly, a fuel cell peak power density of 1.174 W cm−2 is obtained at 80 °C by using SIPN- c QSEBS/QPPO-10 as the separator. Compared with original cross-linked c QSEBS, the semi-interpenetrating network AEM of SIPN- c QSEBS/QPPO-10 exhibits enhanced mechanical properties, improved ionic conductivity and elevated fuel cell performance. [Display omitted] • Highly transparent SIPN AEMs based on PPO and SEBS backbones are prepared. • Good balance achieves among conductivity, mechanical properties and chemical stability. • An AEMFC performance of 1.174 W cm−2 for SIPN- c QSEBS/QPPO-10 is obtained. [ABSTRACT FROM AUTHOR]

In order to investigate the relationship between the side chain topology of comb-shaped anion exchange membranes (AEMs) and membranes properties, two types of hydrophobic side chains attached AEMs that based on QAPPO are synthesized, namely side chains grafted onto backbones and side chains tethered to cations, resulting in A x SB -QAPPO and A x SC -QAPPO AEMs, respectively. Compared with A x SC -QAPPO, the side chains in A x SB -QAPPO AEMs are more inclined to facilitate the membranes to form broad and interconnected ion channels, promoting ion conduction and providing more free volume for the external water to enter the membranes, which are benefit to improving the ionic conductivity and chemical stability of the A x SB -QAPPO samples. At 80 °C, the OH− conductivity of A 8 SB -QAPPO is 101.2 mS cm−1, while the values for A 8 SC -QAPPO and QAPPO are only 56.1 and 48.5 mS cm−1 respectively. After the stability test, the weight and IC retentions of A 8 SB -QAPPO are 83.0% and 77.0%, respectively, while the values for A 8 SC -QAPPO are 76.5% and 68.0%, respectively, and the values for QAPPO are 56.0% and 42.0%, respectively. Besides, the influence of side chain length on the membranes properties is studied. The chemical stability for both A x SB -QAPPO and A x SC -QAPPO AEMs is enhanced by increasing the side chain length from 5 to 14. After the stability test, the IEC retentions of A 5 SB -QAPPO, A 8 SB -QAPPO, A 14 SB -QAPPO, A 5 SC -QAPPO, A 8 SC -QAPPO and A 14 SC -QAPPO are 60.0%, 78.0%, 90.0%, 49.0%, 70.0% and 75.0%, respectively. While for ionic conductivity, the AEMs with the side chain length of 8 exhibit the highest OH− conductivity. Hence, we speculate that the comb-shaped AEMs with hydrophobic side chains attached to backbones (A x SB -QAPPO) are superior to the membranes with the side chains linked to cations (A x SC -QAPPO), and the membranes performance can be further optimized by adjusting the side chain length. [Display omitted] • SC -type AEMs (A x SC -QAPPO) and SB- type AEMs (A x SB -QAPPO) with different length of side chain that based on QAPPO were synthesized successfully. • An important insight into the relationship between the side chain topology of comb-shaped AEMs and membranes properties was offered. • A x SB -QAPPO samples showed higher ionic conductivity and chemical stability than those of (A x SC -QAPPO) AEMs. [ABSTRACT FROM AUTHOR]

In order to achieve a better trade-off among ionic conductivity, mechanical strength and chemical stability, a series of novel aggregated and ionic cross-linked anion exchange membranes (AEMs) are recommended, namely, ac S 6 QAPSF, ac S 8 QAPSF and ac S 10 QAPSF. Cross-linked network shoulders the responsibility to toughen the ac S x QAPSF. Appropriate micro-morphology is responsible for facilitating the conduction of OH− and improving the alkaline stability of the ac S x QAPSF. Compared with the original QAPSF, ac S x QAPSF membranes exhibit much better properties. Specifically, for ac S 8 QAPSF, a high OH− conductivity of 90.5 mS cm−1 is achieved at 80 °C, with the swelling degree of 10.0%. The tensile strength and elongation at break of wet ac S 8 QAPSF at 25 °C are 23.9 Mpa and 21.1%, respectively. After testing in 1 M NaOH at 80 °C for 30 days, the weight loss of ac S 8 QAPSF is 8.0%, with the losses of tensile strength and elongation at break of 13.8% and 13.3%, respectively. Its IEC and IC retentions are 92.0% and 90.5%, respectively. For ac S 8 QAPSF, a fuel cell peak power density of 0.612 W cm−2 is obtained at 60 °C. While for QAPSF, its fuel cell peak power density is only 0.101 W cm−2, and the film is cracked after the 30 days stability test. The unique ac S x QAPSF membrane can alleviate the tradeoff among ionic conductivity, mechanical strength and chemical stability. Image 1 • Novel aggregated and ionic cross-linked AEMs based on PSF are synthesized. • An important insight into the design of AEMs with high performance is provided. • The fuel cell of ac S 8 QAPSF achieved a peak power density of 612 mW cm−2 at 60 °C. [ABSTRACT FROM AUTHOR]