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A New Alkali‐Stable Phosphonium Cation Based on Fundamental Understanding of Degradation Mechanisms
Author(s) -
Zhang Bingzi,
Kaspar Robert B.,
Gu Shuang,
Wang Junhua,
Zhuang Zhongbin,
Yan Yushan
Publication year - 2016
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201600468
Subject(s) - phosphonium , cationic polymerization , chemistry , alkali metal , tris , phosphonium salt , hydroxide , degradation (telecommunications) , kinetics , medicinal chemistry , inorganic chemistry , salt (chemistry) , polymer chemistry , organic chemistry , telecommunications , biochemistry , physics , quantum mechanics , computer science
Highly alkali‐stable cationic groups are a critical component of hydroxide exchange membranes (HEMs). To search for such cations, we studied the degradation kinetics and mechanisms of a series of quaternary phosphonium (QP) cations. Benzyl tris(2,4,6‐trimethoxyphenyl)phosphonium [BTPP‐(2,4,6‐MeO)] was determined to have higher alkaline stability than the benchmark cation, benzyl trimethylammonium (BTMA). A multi‐step methoxy‐triggered degradation mechanism for BTPP‐(2,4,6‐MeO) was proposed and verified. By replacing methoxy substituents with methyl groups, a superior QP cation, methyl tris(2,4,6‐trimethylphenyl)phosphonium [MTPP‐(2,4,6‐Me)] was developed. MTPP‐(2,4,6‐Me) is one of the most stable cations reported to date, with <20 % degradation after 5000 h at 80 °C in a 1 m KOD in CD 3 OD/D 2 O (5:1 v / v ) solution.