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Oxidative Degradation of Nadic-End-Capped PolyimidesThe oxidative degradation of PMR (for polymerization of monomeric reactants) polyimides at elevated temperatures was followed by cross-polarized magic angle spinning (Cp-MAS) NMR. C-13 labeling of selected sites in the polymers allowed for direct observation of the transformations arising from oxidation processes. As opposed to model compound studies, the reactions were followed directly in the polymer. The labeling experiments confirm the previously reported oxidation of the methylene carbon to ketone in the methylenedianiline portion of the polymer chain. They also show the formation of two other oxidized species, acid and ester, from this same carbon. In addition, the technique provides the first evidence of the kind of degradation reactions that are occurring in the nadic end caps. Several PMR formulations containing moieties determined to be present after oxidation, as suggested by the labeling study, were synthesized. Weight loss, FTIR, and natural abundance NMR of these derivatives were followed during aging. In this way, weight loss could be related to the observed transformations.
Document ID
19990081161
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Meador, Mary Ann B.
(NASA Lewis Research Center Cleveland, OH United States)
Johnston, J. Christopher
(NASA Lewis Research Center Cleveland, OH United States)
Cavano, Paul J.
(Case Western Reserve Univ. Cleveland, OH United States)
Frimer, Aryeh A.
(Bar-Ilan Univ. Ramat-Gan, Israel)
Date Acquired
August 19, 2013
Publication Date
January 1, 1997
Publication Information
Publication: Macromolecules
Publisher: American Chemical Society
Volume: 30
Issue: 11
ISSN: S0024-9297
Subject Category
Nonmetallic Materials
Distribution Limits
Public
Copyright
Other

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