Highly conductive hydroxide exchange membranes containing fluorene-units tethered with dual pairs of quaternary piperidinium cations
Allushi, Andrit LU ; Pham, Thanh Huong LU and Jannasch, Patric LU
(2021)
In Journal of Membrane Science
632.
- Abstract
- In the pursuit of anion exchange membranes (AEMs) with high alkaline stability and hydroxide conductivity, we have prepared and characterized a series of poly(fluorene alkylene)s in which each fluorene unit was functionalized with dual pairs of quaternary piperidinium cations on flexible alkyl spacer chains. First, ether-free precursor polymers were synthesized in superacid mediated polyhydroxyalkylations of 2,2,2-trifluoroacetophenone, 9,9-dimethyl-2,7-diphenyl-9H-fluorene, and different amounts of 2,7-dibromo-9,9-bis(6-bromohexyl)-fluorene to regulate the degree of bromoalkylation. Subsequently, the bromoalkyl side chains were utilized to introduce bis-piperidinium (bisPip) cations via Menshutkin reactions. These materials formed... (More)
- In the pursuit of anion exchange membranes (AEMs) with high alkaline stability and hydroxide conductivity, we have prepared and characterized a series of poly(fluorene alkylene)s in which each fluorene unit was functionalized with dual pairs of quaternary piperidinium cations on flexible alkyl spacer chains. First, ether-free precursor polymers were synthesized in superacid mediated polyhydroxyalkylations of 2,2,2-trifluoroacetophenone, 9,9-dimethyl-2,7-diphenyl-9H-fluorene, and different amounts of 2,7-dibromo-9,9-bis(6-bromohexyl)-fluorene to regulate the degree of bromoalkylation. Subsequently, the bromoalkyl side chains were utilized to introduce bis-piperidinium (bisPip) cations via Menshutkin reactions. These materials formed transparent and mechanically strong AEMs upon casting. At 80 °C, the hydroxide conductivity of bisPip AEMs reached 85 and 150 mS cm–1 at ion-exchange capacities (IECs) of 2.0 and 2.8 mequiv g–1, respectively. Moreover, the bisPip AEMs showed high alkaline stability with an ionic loss of merely 6% following immersion in 5 M aq. NaOH solution for a period of 168 h at IEC = 2.8 mequiv g–1. Under these conditions, 1H NMR data indicated that a β-hydrogen in an alkyl spacer chain was about 8 times more susceptible to attacks by hydroxide ions than a β-hydrogen in a piperidinium ring. In comparison, corresponding AEMs with fluorene units functionalized with monoPip cations (i.e., a single pair of piperidinium cations per fluorine unit) showed lower conductivity and alkaline stability under the same conditions, demonstrating the advantage of locally concentrating the cations in the polymer structure by employing
bisPip side chains. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/2cddfde7-918b-4b1d-a1aa-78bab743681b
- author
- Allushi, Andrit
LU
; Pham, Thanh Huong
LU
and Jannasch, Patric
LU
- organization
- publishing date
- 2021-08-15
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Anion exchange membrane, Hydroxide conductivity, Alkaline stability, Anion exchange membrane fuel cell, Polyhydroxyalkylation
- in
- Journal of Membrane Science
- volume
- 632
- article number
- 119376
- pages
- 40 pages
- publisher
- Elsevier
- external identifiers
-
- scopus:85104917692
- ISSN
- 0376-7388
- DOI
- 10.1016/j.memsci.2021.119376
- language
- English
- LU publication?
- yes
- additional info
- Available online 24 April 2021
- id
- 2cddfde7-918b-4b1d-a1aa-78bab743681b
- date added to LUP
- 2020-11-29 20:29:02
- date last changed
- 2022-04-26 22:10:32
@article{2cddfde7-918b-4b1d-a1aa-78bab743681b,
abstract = {{In the pursuit of anion exchange membranes (AEMs) with high alkaline stability and hydroxide conductivity, we have prepared and characterized a series of poly(fluorene alkylene)s in which each fluorene unit was functionalized with dual pairs of quaternary piperidinium cations on flexible alkyl spacer chains. First, ether-free precursor polymers were synthesized in superacid mediated polyhydroxyalkylations of 2,2,2-trifluoroacetophenone, 9,9-dimethyl-2,7-diphenyl-9H-fluorene, and different amounts of 2,7-dibromo-9,9-bis(6-bromohexyl)-fluorene to regulate the degree of bromoalkylation. Subsequently, the bromoalkyl side chains were utilized to introduce bis-piperidinium (bisPip) cations via Menshutkin reactions. These materials formed transparent and mechanically strong AEMs upon casting. At 80 °C, the hydroxide conductivity of bisPip AEMs reached 85 and 150 mS cm<sup>–1</sup> at ion-exchange capacities (IECs) of 2.0 and 2.8 mequiv g<sup>–1</sup>, respectively. Moreover, the bisPip AEMs showed high alkaline stability with an ionic loss of merely 6% following immersion in 5 M aq. NaOH solution for a period of 168 h at IEC = 2.8 mequiv g<sup>–1</sup>. Under these conditions, <sup>1</sup>H NMR data indicated that a β-hydrogen in an alkyl spacer chain was about 8 times more susceptible to attacks by hydroxide ions than a β-hydrogen in a piperidinium ring. In comparison, corresponding AEMs with fluorene units functionalized with monoPip cations (i.e., a single pair of piperidinium cations per fluorine unit) showed lower conductivity and alkaline stability under the same conditions, demonstrating the advantage of locally concentrating the cations in the polymer structure by employing<br/>bisPip side chains.}},
author = {{Allushi, Andrit and Pham, Thanh Huong and Jannasch, Patric}},
issn = {{0376-7388}},
keywords = {{Anion exchange membrane; Hydroxide conductivity; Alkaline stability; Anion exchange membrane fuel cell; Polyhydroxyalkylation}},
language = {{eng}},
month = {{08}},
publisher = {{Elsevier}},
series = {{Journal of Membrane Science}},
title = {{Highly conductive hydroxide exchange membranes containing fluorene-units tethered with dual pairs of quaternary piperidinium cations}},
url = {{http://dx.doi.org/10.1016/j.memsci.2021.119376}},
doi = {{10.1016/j.memsci.2021.119376}},
volume = {{632}},
year = {{2021}},
}