Joseph, Dickson Krishnan, N. Nambi Henkensmeier, Dirk Jang, Jong Hyun Choi, Sun Hee Kim, Hyoung-Juhn Han, Jonghee Nam, Suk Woo 2024-01-20T02:32:38Z 2024-01-20T02:32:38Z 2021-09-05 2017-01 2050-7488 https://pubs.kist.re.kr/handle/201004/123261 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 degrees 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. English ROYAL SOC CHEMISTRY Thermal crosslinking of PBI/sulfonated polysulfone based blend membranes Article 10.1039/c6ta07653j 1 JOURNAL OF MATERIALS CHEMISTRY A, v.5, no.1, pp.409 - 417 JOURNAL OF MATERIALS CHEMISTRY A 5 1 409 417 N scie scopus 000391572200043 2-s2.0-85006866994 Chemistry, Physical Energy & Fuels Materials Science, Multidisciplinary Chemistry Energy & Fuels Materials Science Article POLY(ETHER ETHER KETONE) PEM FUEL-CELLS PHOSPHORIC-ACID ELECTROLYTE MEMBRANES POLYMER ELECTROLYTE PBI MEMBRANES TEMPERATURE POLYBENZIMIDAZOLE STABILITY DEGRADATION polybenzimidazole membranes crosslinking Friedel-Crafts reaction HT PEMFC