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Properties and degradation of hydrocarbon fuel cell membranes: a comparative study of sulfonated poly(arylene ether sulfone)s with different positions of the acid groups

Takamuku, Shogo LU and Jannasch, Patric LU (2012) In Polymer Chemistry 3(5). p.1202-1214
Abstract
Sulfonated fully aromatic polymers with different positions of the acid groups, but with an identical polymer backbone, have been investigated and compared with respect to their properties as proton-exchange membranes. Three different series of sulfonated poly(arylene ether sulfone)s (SPAES) having the same backbone structure were prepared from 4,4’-dichlorodiphenyl sulfone (DCDPS) and 4,4’-dihydroxybiphenyl (BP), each series comprising three levels of the ion exchange capacity (IEC). The first series of SPAES had the sulfonic acid groups placed in ortho positions to the ether bridges (oeSPAES) and were prepared through post-polymerization sulfonation. The second and third series of SPAES carried the sulfonic acid groups in meta (msSPAES)... (More)
Sulfonated fully aromatic polymers with different positions of the acid groups, but with an identical polymer backbone, have been investigated and compared with respect to their properties as proton-exchange membranes. Three different series of sulfonated poly(arylene ether sulfone)s (SPAES) having the same backbone structure were prepared from 4,4’-dichlorodiphenyl sulfone (DCDPS) and 4,4’-dihydroxybiphenyl (BP), each series comprising three levels of the ion exchange capacity (IEC). The first series of SPAES had the sulfonic acid groups placed in ortho positions to the ether bridges (oeSPAES) and were prepared through post-polymerization sulfonation. The second and third series of SPAES carried the sulfonic acid groups in meta (msSPAES) and ortho (osSPAES) positions to the sulfone bridges, respectively, and were prepared by polycondensations of mixtures of BP, DCDPS and either 3,3’-disulfonated or 2,2’-disulfonated DCDPS, respectively. The latter monomer was synthesized via lithiation-sulfination-oxidation of DCDPS. Analysis of solvent cast membranes showed that the osSPAES copolymers had a high dimensional stability in water up to 100 ˚C, even at high ionic contents. Moreover, the osSPAES membranes were better at retaining conductivity at reduced relative humidity than the msSPAES and oeSPAES membranes. Thermogravimetry of the membranes in the acid form under air indicated no significant differences based on the placement of the sulfonic acid groups. The resistance towards radical attack was analyzed by 1H NMR spectroscopy after immersing the membranes in Fenton’s reagent at 60 ˚C, and the ability to retain IEC was found to increase in the order oeSPAES< msSPAES< osSPAES. Membrane stability was also studied in an accelerated hydrolysis test by immersing the membranes in 0.1 M aq. HCl at 200 ˚C in a sealed vessel. The results showed a dramatic loss of sulfonic acid in the oeSPAES membranes, presumably activated by the proximity of the ether bridges. Careful 1H NMR analysis also revealed that the osSPAES polymers degraded by scission of the sulfone bridges. The position of the sulfonic acid groups ortho to the sulfone bridges seemingly destabilized the latter under the severe conditions employed in the test. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
polyelectrolytes, statistical copolymers, polysulfones, proton-conducting fuel cell membranes, sulfonation, durability
in
Polymer Chemistry
volume
3
issue
5
pages
1202 - 1214
publisher
Royal Society of Chemistry
external identifiers
  • wos:000302315800015
  • scopus:84859749037
ISSN
1759-9954
DOI
10.1039/C2PY00611A
language
English
LU publication?
yes
id
c224956d-cc0c-4ba6-a781-cdd199b83a78 (old id 2339158)
alternative location
http://pubs.rsc.org/en/Content/ArticleLanding/2012/PY/C2PY00611A
date added to LUP
2012-03-06 17:26:57
date last changed
2017-09-10 03:28:21
@article{c224956d-cc0c-4ba6-a781-cdd199b83a78,
  abstract     = {Sulfonated fully aromatic polymers with different positions of the acid groups, but with an identical polymer backbone, have been investigated and compared with respect to their properties as proton-exchange membranes. Three different series of sulfonated poly(arylene ether sulfone)s (SPAES) having the same backbone structure were prepared from 4,4’-dichlorodiphenyl sulfone (DCDPS) and 4,4’-dihydroxybiphenyl (BP), each series comprising three levels of the ion exchange capacity (IEC). The first series of SPAES had the sulfonic acid groups placed in ortho positions to the ether bridges (oeSPAES) and were prepared through post-polymerization sulfonation. The second and third series of SPAES carried the sulfonic acid groups in meta (msSPAES) and ortho (osSPAES) positions to the sulfone bridges, respectively, and were prepared by polycondensations of mixtures of BP, DCDPS and either 3,3’-disulfonated or 2,2’-disulfonated DCDPS, respectively. The latter monomer was synthesized via lithiation-sulfination-oxidation of DCDPS. Analysis of solvent cast membranes showed that the osSPAES copolymers had a high dimensional stability in water up to 100 ˚C, even at high ionic contents. Moreover, the osSPAES membranes were better at retaining conductivity at reduced relative humidity than the msSPAES and oeSPAES membranes. Thermogravimetry of the membranes in the acid form under air indicated no significant differences based on the placement of the sulfonic acid groups. The resistance towards radical attack was analyzed by 1H NMR spectroscopy after immersing the membranes in Fenton’s reagent at 60 ˚C, and the ability to retain IEC was found to increase in the order oeSPAES&lt; msSPAES&lt; osSPAES. Membrane stability was also studied in an accelerated hydrolysis test by immersing the membranes in 0.1 M aq. HCl at 200 ˚C in a sealed vessel. The results showed a dramatic loss of sulfonic acid in the oeSPAES membranes, presumably activated by the proximity of the ether bridges. Careful 1H NMR analysis also revealed that the osSPAES polymers degraded by scission of the sulfone bridges. The position of the sulfonic acid groups ortho to the sulfone bridges seemingly destabilized the latter under the severe conditions employed in the test.},
  author       = {Takamuku, Shogo and Jannasch, Patric},
  issn         = {1759-9954},
  keyword      = {polyelectrolytes,statistical copolymers,polysulfones,proton-conducting fuel cell membranes,sulfonation,durability},
  language     = {eng},
  number       = {5},
  pages        = {1202--1214},
  publisher    = {Royal Society of Chemistry},
  series       = {Polymer Chemistry},
  title        = {Properties and degradation of hydrocarbon fuel cell membranes: a comparative study of sulfonated poly(arylene ether sulfone)s with different positions of the acid groups},
  url          = {http://dx.doi.org/10.1039/C2PY00611A},
  volume       = {3},
  year         = {2012},
}