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Correlation of the crystal structure and solid‐state 13 C NMR spectrum of pyromellitic dianhydride
Author(s) -
Wolfe Roger A.,
Schwartz Willis T.,
Dinan Frank J.
Publication year - 1991
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260290506
Subject(s) - chemistry , pyromellitic dianhydride , differential scanning calorimetry , melting point , crystallography , crystal structure , thermodynamics , organic chemistry , physics , polyimide , layer (electronics)
The interatomic distances for crystalline pyromellitic dianhydride (PMDA) were calculated from x‐ray crystallographic data. The CP‐MAS 13 C NMR spectrum of PMDA was found to be consistent with and accountable for in terms of these distances after literature assignment errors were corrected. An anomalous peak was observed in the differential scanning calorimetry thermogram of PMDA. The entropy change associated with this transition indicates that a two‐fold change in symmetry occurs approximately 60°C below the melting point of PMDA. Attempts to observe this transition by CP‐MAS 13 C NMR were unsuccessful.