Functionalizing polystyrene with N-alicyclic piperidine-based cations via Friedel-Crafts alkylation for highly alkali-stable anion-exchange membranes
Olsson, Joel LU ; Pham, Thanh Huong LU and Jannasch, Patric LU
(2020)
In Macromolecules
53(12).
p.4722-4732
- Abstract
- Different anion-exchange membranes (AEMs) based on polystyrene (PS) carrying benzyltrimethyl ammonium cations are currently developed for use in alkaline fuel cells and water electrolyzers. However, the stability of these state-of-the-art cations needs to be further improved. Here, we introduce highly alkali-stable mono- and spirocyclic piperidine-based cations onto PS by first performing a superacid mediated Friedel-Crafts alkylation using 2-(piperidine-4-yl)propane-2-ol. This is followed by quaternization of the piperidine rings either using iodomethane to produce N,N-dimethylpiperidinium cations or cyclo-quaternizations using 1,5-dibromopentane and 1,4-dibromobutane, respectively, to obtain N-spirocyclic quaternary... (More)
- Different anion-exchange membranes (AEMs) based on polystyrene (PS) carrying benzyltrimethyl ammonium cations are currently developed for use in alkaline fuel cells and water electrolyzers. However, the stability of these state-of-the-art cations needs to be further improved. Here, we introduce highly alkali-stable mono- and spirocyclic piperidine-based cations onto PS by first performing a superacid mediated Friedel-Crafts alkylation using 2-(piperidine-4-yl)propane-2-ol. This is followed by quaternization of the piperidine rings either using iodomethane to produce N,N-dimethylpiperidinium cations or cyclo-quaternizations using 1,5-dibromopentane and 1,4-dibromobutane, respectively, to obtain N-spirocyclic quaternary ammonium cations. Thus, it is possible to functionalize up to 27% of the styrene units with piperidine rings, and subsequently achieve complete quaternization. The synthetic approach ensures that all the sensitive β-hydrogens of the cations are present in ring structures to provide high stability. AEMs based on these polymers show high alkaline stability and less than 5% ionic loss was observed by 1H NMR spectroscopy after 30 days in 2 M aq. NaOH at 90 °C. AEMs functionalized with N,N-dimethylpiperidinium cations show a higher stability than the ones carrying N-spirocyclic quaternary ammonium. Careful analysis of the latter revealed that the rings formed in the cyclo-quaternization are more prone to degrade via Hofmann elimination than the rings introduced in the Friedel-Crafts reaction. AEMs with an ion exchange capacity of 1.5 meq g-1 reach a hydroxide conductivity of 106 mS cm-1 at 80 °C under fully hydrated conditions. The AEMs are further tuned and improved by blending with polybenzimidazole (PBI). For example, an AEM containing 2 wt% PBI shows reduced water uptake and much improved robustness during handling, and reaches 71 mS cm-1 at 80 °C. The study demonstrates that the critical alkaline stability of PS-containing AEMs can be significantly enhanced by replacing the benchmark benzyltrimethyl ammonium cations with N-alicyclic piperidine-based cations. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/1e33ffad-9b82-475c-ae2b-fcffe3566f8d
- author
- Olsson, Joel
LU
; Pham, Thanh Huong
LU
and Jannasch, Patric
LU
- organization
- publishing date
- 2020
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Macromolecules
- volume
- 53
- issue
- 12
- pages
- 11 pages
- publisher
- The American Chemical Society (ACS)
- external identifiers
-
- scopus:85086249345
- pmid:32905320
- ISSN
- 0024-9297
- DOI
- 10.1021/acs.macromol.0c00201
- language
- English
- LU publication?
- yes
- additional info
- Publication Date: June 1, 2020
- id
- 1e33ffad-9b82-475c-ae2b-fcffe3566f8d
- date added to LUP
- 2020-05-15 18:25:44
- date last changed
- 2022-04-18 22:12:08
@article{1e33ffad-9b82-475c-ae2b-fcffe3566f8d,
abstract = {{Different anion-exchange membranes (AEMs) based on polystyrene (PS) carrying benzyltrimethyl ammonium cations are currently developed for use in alkaline fuel cells and water electrolyzers. However, the stability of these state-of-the-art cations needs to be further improved. Here, we introduce highly alkali-stable mono- and spirocyclic piperidine-based cations onto PS by first performing a superacid mediated Friedel-Crafts alkylation using 2-(piperidine-4-yl)propane-2-ol. This is followed by quaternization of the piperidine rings either using iodomethane to produce <i>N</i>,<i>N</i>-dimethylpiperidinium cations or cyclo-quaternizations using 1,5-dibromopentane and 1,4-dibromobutane, respectively, to obtain N-spirocyclic quaternary ammonium cations. Thus, it is possible to functionalize up to 27% of the styrene units with piperidine rings, and subsequently achieve complete quaternization. The synthetic approach ensures that all the sensitive β-hydrogens of the cations are present in ring structures to provide high stability. AEMs based on these polymers show high alkaline stability and less than 5% ionic loss was observed by <sup>1</sup>H NMR spectroscopy after 30 days in 2 M aq. NaOH at 90 °C. AEMs functionalized with <i>N</i>,<i>N</i>-dimethylpiperidinium cations show a higher stability than the ones carrying <i>N</i>-spirocyclic quaternary ammonium. Careful analysis of the latter revealed that the rings formed in the cyclo-quaternization are more prone to degrade via Hofmann elimination than the rings introduced in the Friedel-Crafts reaction. AEMs with an ion exchange capacity of 1.5 meq g<sup>-1</sup> reach a hydroxide conductivity of 106 mS cm<sup>-1</sup> at 80 °C under fully hydrated conditions. The AEMs are further tuned and improved by blending with polybenzimidazole (PBI). For example, an AEM containing 2 wt% PBI shows reduced water uptake and much improved robustness during handling, and reaches 71 mS cm<sup>-1</sup> at 80 °C. The study demonstrates that the critical alkaline stability of PS-containing AEMs can be significantly enhanced by replacing the benchmark benzyltrimethyl ammonium cations with <i>N</i>-alicyclic piperidine-based cations.}},
author = {{Olsson, Joel and Pham, Thanh Huong and Jannasch, Patric}},
issn = {{0024-9297}},
language = {{eng}},
number = {{12}},
pages = {{4722--4732}},
publisher = {{The American Chemical Society (ACS)}},
series = {{Macromolecules}},
title = {{Functionalizing polystyrene with <i>N</i>-alicyclic piperidine-based cations via Friedel-Crafts alkylation for highly alkali-stable anion-exchange membranes}},
url = {{http://dx.doi.org/10.1021/acs.macromol.0c00201}},
doi = {{10.1021/acs.macromol.0c00201}},
volume = {{53}},
year = {{2020}},
}