TY - JOUR
T1 - Anion exchange membranes with twisted poly(terphenylene) backbone
T2 - Effect of the N-cyclic cations
AU - Wang, Xiuqin
AU - Lin, Chenxiao
AU - Gao, Yang
AU - Lammertink, Rob G.H.
N1 - Funding Information:
Financial support from the Guangdong Basic and Applied Basic Research Fund ( 2019A1515111188 ) and China Scholarship Council (CSC) are gratefully acknowledged. This work is part of the Vici project STW 016.160.312 which is financed by the Netherlands Organisation for Scientific Research (NWO).
Funding Information:
In order to achieve high conductivity, a microphase separated structure in the membranes is suggested [3,36]. It is likely that the presence of the twisted backbone would allow the polymer chain to form a compact structure and promote the self-assembly of the ionic groups [31]. Besides, the size/type of the cations could also affect the morphology of the membranes [37,38]. Herein, TEM and SAXS were applied to investigate the morphology of the as-prepared AEMs. As shows in Fig. 4a?c, the dark and bright areas refer to the hydrophilic domains and hydrophobic domains, respectively. The degree of microphase separation in m-TPNPiQA is more obvious in the TEM than for the other two AEMs (and also supported by the SAXS pattern). It is found that increasing the steric hindrance of cations go against to the degree of microphase separation. The smaller cationic groups improve ion clustering, leading to the formation of larger and more connected ion pathway channels. The reason may be that the rigidity of the cation increased with increasing steric hindrance which could be harmful to the self-assembly of the polymer chain. The phase separation behavior of commercial membrane FAA-3-50 was different from the as-prepared AEMs due to the difference in chemical materials, where the contrast of bright domain and dark domain is less regular. This phenomenon is further visible from their corresponding FFT images (Fig. 4a'-c') which were directly transferred from the TEM images. The obvious scatter rings represent the periodic distance (d) of ionic segregation behavior inside the membrane. It becomes more obvious with decreasing steric hindrance of the cations. The long period of the m-TPNPiQA was approximately 1.53 nm and a weaker wider ring was also observed with d of 1.31 nm. A somewhat similar FFT was also shown in m-TPNPyQA with corresponding d observed at 1.01 nm and 0.82 nm. The m-TPNBeQA and FAA-3-50 only show a diffuse scatter ring.Lammertink reports financial support was provided by Netherlands Organisation for Scientific Research (NWO). Wang reports financial support was provided by China Scholarship Council. Lin reports financial support was provided by Guangdong Basic and Applied Basic Research Fund.Financial support from the Guangdong Basic and Applied Basic Research Fund (2019A1515111188) and China Scholarship Council (CSC) are gratefully acknowledged. This work is part of the Vici project STW 016.160.312 which is financed by the Netherlands Organisation for Scientific Research (NWO).
Publisher Copyright:
© 2021 The Authors
PY - 2021/10/1
Y1 - 2021/10/1
N2 - In order to investigate the relationship towards the cationic structures and ion exchange membrane performance, three kinds of twisted poly(terphenylene)-based anion exchange membranes (AEMs) with N-cyclic cations were prepared via facile Friedel-Crafts type polycondensation and quaternization. The steric hindrance of the N-cyclic cations is gradually increased from the small piperidinium to the sterically protected N-spirocyclic quaternary ammonium (QA). The twisted poly(terphenylene)s backbone promotes the self-assembly of the polymer chain and forms a microphase separated morphology, resulting in a highest conductivity of 68.7 mS cm−1 (80 °C) for the polymer tethered with piperidinium groups (m-TPNPiQA). The relative conductivity (conductivity/swelling ratio) of m-TPNPiQA is even higher than that of the commercial Fumapem FAA-3-50 membrane. Increasing the size of the QA is helpful to constrain water absorption and related swelling but has a negative effect on the chemical stability. β-Hofmann elimination degradation is observed for all of the AEMs during a stability test by 1H NMR analysis. The m-TPNPiQA demonstrates less than 6% ionic exchange capacity loss after 240 h in 5 M NaOH solution at 80 °C. The results demonstrated that the membrane performance is associated well with the features of the cationic groups. A high performance AEM can be achieved by grafting appropriate cations onto aryl ether-free backbone.
AB - In order to investigate the relationship towards the cationic structures and ion exchange membrane performance, three kinds of twisted poly(terphenylene)-based anion exchange membranes (AEMs) with N-cyclic cations were prepared via facile Friedel-Crafts type polycondensation and quaternization. The steric hindrance of the N-cyclic cations is gradually increased from the small piperidinium to the sterically protected N-spirocyclic quaternary ammonium (QA). The twisted poly(terphenylene)s backbone promotes the self-assembly of the polymer chain and forms a microphase separated morphology, resulting in a highest conductivity of 68.7 mS cm−1 (80 °C) for the polymer tethered with piperidinium groups (m-TPNPiQA). The relative conductivity (conductivity/swelling ratio) of m-TPNPiQA is even higher than that of the commercial Fumapem FAA-3-50 membrane. Increasing the size of the QA is helpful to constrain water absorption and related swelling but has a negative effect on the chemical stability. β-Hofmann elimination degradation is observed for all of the AEMs during a stability test by 1H NMR analysis. The m-TPNPiQA demonstrates less than 6% ionic exchange capacity loss after 240 h in 5 M NaOH solution at 80 °C. The results demonstrated that the membrane performance is associated well with the features of the cationic groups. A high performance AEM can be achieved by grafting appropriate cations onto aryl ether-free backbone.
KW - UT-Hybrid-D
U2 - 10.1016/j.memsci.2021.119525
DO - 10.1016/j.memsci.2021.119525
M3 - Article
SN - 0376-7388
VL - 635
JO - Journal of membrane science
JF - Journal of membrane science
M1 - 119525
ER -