Effects of the N-alicyclic cation and backbone structures on the performance of poly(terphenyl)-based hydroxide exchange membranes
Pham, Thanh Huong LU ; Olsson, Joel LU and Jannasch, Patric LU
(2019)
In Journal of Materials Chemistry A
7(26).
p.15895-15906
- Abstract
Hydroxide ion conducting poly(terphenyl alkylene)s functionalized with piperidine-based quaternary ammonium cations were synthesized via superacid-catalyzed polyhydroxyalkylations. By employing different synthetic strategies, we have systematically varied the structures of the cation and the backbone polymer to study the effects on morphology, stability and hydroxide conductivity. Two monomers were initially prepared by attaching 4-benzylpiperidine groups to trifluororacetophenone and m-terphenyl, respectively, through Suzuki coupling reactions. Polymerizations followed by quaternizations were then carried out to obtain poly(terphenyl alkylene)s with approximately the same ionic contents. These contained either m- or... (More)
Hydroxide ion conducting poly(terphenyl alkylene)s functionalized with piperidine-based quaternary ammonium cations were synthesized via superacid-catalyzed polyhydroxyalkylations. By employing different synthetic strategies, we have systematically varied the structures of the cation and the backbone polymer to study the effects on morphology, stability and hydroxide conductivity. Two monomers were initially prepared by attaching 4-benzylpiperidine groups to trifluororacetophenone and m-terphenyl, respectively, through Suzuki coupling reactions. Polymerizations followed by quaternizations were then carried out to obtain poly(terphenyl alkylene)s with approximately the same ionic contents. These contained either m- or p-terphenyl backbone units, and were tethered with monocyclic N,N-dimethylpiperidinium (DMP) or spirocyclic 6-azonia-spiro[5,5]undecane-6-ium (ASU) cations placed on either the stiff terphenyl or the more flexible alkylene units along the backbone. Polymer chain flexibility and functionalization with DMP cations were found to promote ionic clustering and conductivity. Hence, a membrane based on a m-terphenyl backbone tethered with DMP on pendant phenyl groups achieveda hydroxide conductivity of 146 mS cm-1 at 80 oC. While the thermal stability was significantly higher forASU-functionalized HEMs, the alkaline stability was highest for the ones carrying DMP cations, which showed less than 5% ionic loss after 720 h in 2 M NaOH at 90 oC. After 168 h at 120 oC, 1H NMR analysis suggested that the DMP cation degraded by a combination of β-Hofmann elimination and methyl substitution. Overall, the results of the study demonstrated that the structural features of the present polymers provided high alkaline stability, most probably due to aryl ether-free backbones, and that all the β-protons of the DMP and ASU cations were placed in 6-membered rings.
(Less)
- author
- Pham, Thanh Huong
LU
; Olsson, Joel
LU
and Jannasch, Patric
LU
- organization
- publishing date
- 2019
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Journal of Materials Chemistry A
- volume
- 7
- issue
- 26
- pages
- 12 pages
- publisher
- Royal Society of Chemistry
- external identifiers
-
- scopus:85068499908
- ISSN
- 2050-7488
- DOI
- 10.1039/C9TA05531B
- language
- English
- LU publication?
- yes
- additional info
- The article was received on 24 May 2019, accepted on 06 Jun 2019 and first published on 06 Jun 2019
- id
- dec9dfe7-f951-4026-9e01-f773ff7e621b
- date added to LUP
- 2019-06-06 20:20:18
- date last changed
- 2022-06-13 20:27:30
@article{dec9dfe7-f951-4026-9e01-f773ff7e621b,
abstract = {{<p>Hydroxide ion conducting poly(terphenyl alkylene)s functionalized with piperidine-based quaternary ammonium cations were synthesized via superacid-catalyzed polyhydroxyalkylations. By employing different synthetic strategies, we have systematically varied the structures of the cation and the backbone polymer to study the effects on morphology, stability and hydroxide conductivity. Two monomers were initially prepared by attaching 4-benzylpiperidine groups to trifluororacetophenone and <i>m</i>-terphenyl, respectively, through Suzuki coupling reactions. Polymerizations followed by quaternizations were then carried out to obtain poly(terphenyl alkylene)s with approximately the same ionic contents. These contained either <i>m</i>- or <i>p</i>-terphenyl backbone units, and were tethered with monocyclic <i>N,N</i>-dimethylpiperidinium (DMP) or spirocyclic 6-azonia-spiro[5,5]undecane-6-ium (ASU) cations placed on either the stiff terphenyl or the more flexible alkylene units along the backbone. Polymer chain flexibility and functionalization with DMP cations were found to promote ionic clustering and conductivity. Hence, a membrane based on a <i>m</i>-terphenyl backbone tethered with DMP on pendant phenyl groups achieveda hydroxide conductivity of 146 mS cm<sup>-1</sup> at 80 <sup>o</sup>C. While the thermal stability was significantly higher forASU-functionalized HEMs, the alkaline stability was highest for the ones carrying DMP cations, which showed less than 5% ionic loss after 720 h in 2 M NaOH at 90 <sup>o</sup>C. After 168 h at 120 <sup>o</sup>C, <sup>1</sup>H NMR analysis suggested that the DMP cation degraded by a combination of β-Hofmann elimination and methyl substitution. Overall, the results of the study demonstrated that the structural features of the present polymers provided high alkaline stability, most probably due to aryl ether-free backbones, and that all the β-protons of the DMP and ASU cations were placed in 6-membered rings. </p>}},
author = {{Pham, Thanh Huong and Olsson, Joel and Jannasch, Patric}},
issn = {{2050-7488}},
language = {{eng}},
number = {{26}},
pages = {{15895--15906}},
publisher = {{Royal Society of Chemistry}},
series = {{Journal of Materials Chemistry A}},
title = {{Effects of the <i>N</i>-alicyclic cation and backbone structures on the performance of poly(terphenyl)-based hydroxide exchange membranes}},
url = {{http://dx.doi.org/10.1039/C9TA05531B}},
doi = {{10.1039/C9TA05531B}},
volume = {{7}},
year = {{2019}},
}