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Quantum Chemical Analysis of Polyamic Acids and Polyimides
Published in Michael I. Bessonov, Vladimir A. Zubkov, Polyamic Acids and Polyimides, 2020
The foregoing calculations have shown that in a medium with deprotonating properties, imide products should predominate, but in a medium with protonating properties isoimide products would be predominant. On this basis, it is possible to interpret the observed dependence of the chemical structure of the final polymer on the catalytic medium composition. For this purpose, it is necessary to establish the relationship between the predominant deprotonation or protonation of amic acid units and catalytic bath composition. It has been mentioned that acetic anhydride (AA) and trifluoroacetic anhydride (TFA) are most commonly used as dehydration agents. The influence of the catalytic bath composition containing AA or/and TFA and pyridine (Py) on the rate constants of the imide and isoimide ring formation has been studied in detail by Kudryavtzev et al.69 76 77 Some of the results necessary for subsequent presentation are given in Table 13. (For further details see Chapter 1 of this book.)
Polyimide Synthesis and Industrial Applications
Published in Robert R. Luise, of High Temperature Polymers, 1997
The two-step technique (see Table 1) appeared in the 1950s and was the basis for initial development of the aromatic polyimides.1–3 There are two products formed from the amic acid precursor, namely, the polyimide and also the isomeric polyisoimide. The isoimide forms in significant quantities when the conversion proceeds with catalysis by strongly acidic systems such as PCI or trifluoroacetic anhydride, but only in limited quantities thermally or by the use of such agents as acetic anhydride/pyridine. Polyisoimide converts to normal imide at temperatures above 300°C. This chemistry is the basis for such films as Kapton and Upilex S, molding polymers such as Vespel, and the variety of end uses including coatings of chips and wire.
Chemistry and Kinetics of Polyimide Formation
Published in Malay K. Ghosh, K. L. Mittal, Polyimides Fundamentals and Applications, 2018
James M. Sonnett, Thomas P. Gannett
In another paper [106], the imidization of poly(4,4′-oxydiphenylenepyromellitamic acid) with acetic anhydride or trifluoroacetic anhydride, both in the presence and absence of pyridine, was studied. Their result, in terms of relative concentrations and relative rate constants, are summarized in Table 5.
Biobased Support Layers for the Fractionation and Selective Extraction of Lignosulfonates
Published in Solvent Extraction and Ion Exchange, 2020
Marlene Kienberger, Paul Demmelmayer, Michael Weißl, Armin Zankl, Stefan Spirk
For the modification of the cellulose films, trifluoroacetic anhydride (TFAA; CAS 407-25-0) was purchased from Sigma-Aldrich in a purity of > 99%, acetic anhydride (CAS 108-24-7) was purchased in a purity of > 99% from Roth and hexamethyldisilazane (HMDS; CAS 999-97-3) was purchased from Sigma-Aldrich in a quality of > 99%. All chemicals were used as received.