Abstract
Crosslinked polybenzimidazole (PBI) membranes are most often obtained by reacting the nitrogen atoms of PBI with an alkylating agent. These links can be attacked by nucleophiles at elevated temperatures. To avoid N-CH2-links we introduce a new method to crosslink PBI, starting from ionically crosslinked acid/base blend membranes. By heating them to temperatures above say 200 °C, a Friedel-Crafts reaction between sulfonic acid groups and electron rich phenyl groups covalently crosslinks the acid and base components in the blend by chemically stable aromatic sulfone bonds. According to the literature pure PBI can also be cured and a radical mechanism involving air was suggested. We show that PBI can also be cured in an inert atmosphere. We propose that the thermal curing of pure PBI, which necessitates slightly higher temperatures than blend membranes, proceeds via hydrolysis of imidazole to-COOH and diamine, followed by a Friedel-Crafts reaction of the acid. While crosslinks cannot be directly analysed by nmr or IR, our data support the mentioned mechanism. We show the effect of curing temperature and time on membrane properties like solubility, phosphoric acid uptake and mechanical properties, and test a membrane in a fuel cell, proving that the membranes are gas tight and show a good performance.
| Original language | English |
|---|---|
| Pages (from-to) | 409-417 |
| Number of pages | 9 |
| Journal | Journal of Materials Chemistry A |
| Volume | 5 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 2017 |
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ASJC Scopus subject areas
- Chemistry(all)
- Renewable Energy, Sustainability and the Environment
- Materials Science(all)
Cite this
Thermal crosslinking of PBI/sulfonated polysulfone based blend membranes. / Joseph, Dickson; Krishnan, N. Nambi; Henkensmeier, Dirk; Jang, Jong Hyun; Choi, Sun Hee; Kim, Hyoung Juhn; Han, Jonghee; Nam, SukWoo.
In: Journal of Materials Chemistry A, Vol. 5, No. 1, 2017, p. 409-417.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Thermal crosslinking of PBI/sulfonated polysulfone based blend membranes
AU - Joseph, Dickson
AU - Krishnan, N. Nambi
AU - Henkensmeier, Dirk
AU - Jang, Jong Hyun
AU - Choi, Sun Hee
AU - Kim, Hyoung Juhn
AU - Han, Jonghee
AU - Nam, SukWoo
PY - 2017
Y1 - 2017
N2 - Crosslinked polybenzimidazole (PBI) membranes are most often obtained by reacting the nitrogen atoms of PBI with an alkylating agent. These links can be attacked by nucleophiles at elevated temperatures. To avoid N-CH2-links we introduce a new method to crosslink PBI, starting from ionically crosslinked acid/base blend membranes. By heating them to temperatures above say 200 °C, a Friedel-Crafts reaction between sulfonic acid groups and electron rich phenyl groups covalently crosslinks the acid and base components in the blend by chemically stable aromatic sulfone bonds. According to the literature pure PBI can also be cured and a radical mechanism involving air was suggested. We show that PBI can also be cured in an inert atmosphere. We propose that the thermal curing of pure PBI, which necessitates slightly higher temperatures than blend membranes, proceeds via hydrolysis of imidazole to-COOH and diamine, followed by a Friedel-Crafts reaction of the acid. While crosslinks cannot be directly analysed by nmr or IR, our data support the mentioned mechanism. We show the effect of curing temperature and time on membrane properties like solubility, phosphoric acid uptake and mechanical properties, and test a membrane in a fuel cell, proving that the membranes are gas tight and show a good performance.
AB - Crosslinked polybenzimidazole (PBI) membranes are most often obtained by reacting the nitrogen atoms of PBI with an alkylating agent. These links can be attacked by nucleophiles at elevated temperatures. To avoid N-CH2-links we introduce a new method to crosslink PBI, starting from ionically crosslinked acid/base blend membranes. By heating them to temperatures above say 200 °C, a Friedel-Crafts reaction between sulfonic acid groups and electron rich phenyl groups covalently crosslinks the acid and base components in the blend by chemically stable aromatic sulfone bonds. According to the literature pure PBI can also be cured and a radical mechanism involving air was suggested. We show that PBI can also be cured in an inert atmosphere. We propose that the thermal curing of pure PBI, which necessitates slightly higher temperatures than blend membranes, proceeds via hydrolysis of imidazole to-COOH and diamine, followed by a Friedel-Crafts reaction of the acid. While crosslinks cannot be directly analysed by nmr or IR, our data support the mentioned mechanism. We show the effect of curing temperature and time on membrane properties like solubility, phosphoric acid uptake and mechanical properties, and test a membrane in a fuel cell, proving that the membranes are gas tight and show a good performance.
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U2 - 10.1039/c6ta07653j
DO - 10.1039/c6ta07653j
M3 - Article
AN - SCOPUS:85006866994
VL - 5
SP - 409
EP - 417
JO - Journal of Materials Chemistry A
JF - Journal of Materials Chemistry A
SN - 2050-7488
IS - 1
ER -