Effect of structural variations on the thermo‐oxidative stability of aromatic polyimides

Abstract

Polyimides were synthesised from a number of diamines and dianhydrides and their stability determined by thermogravimetric analysis a t 4OO0C in air. Wherever possible high molecular weight films obtained by thermal condensation of the polyamic acid intermediates were studied. If this was not possible, films obtained from acetic acid anhydride ciclised polymers or thermally cured powders were used.A well defined order of stability was observed for the polyimides prepared from pyromellitic diauhydride and a variety of diamines. The simplest and most symmetrical struetures had the greatest thermal stability. Lowest stabilities were observed when linking groups were electronegative in nature. ZUSAMMENFASSUNG:Polyimide wurden aus einer Vielfalt van Diaminen und Dianhydriden hergestellt. Ihre Stabilitat bei 400 "C in Luft wurde durch thermogravimetrische Analyse bestimmt. Wenn moglich, wurden hochmolekulare Filme verwendet, die durch thermische Kondensation der Poly-Amidsaure-Zwischenprodukte erhalten wurden. Wenn dies nicht moglich war, wurden Filme aus Polymeren, die mit Acetanhydrid cyclisiert waren, oder warmebehandelte Pulver untersucht. Fur die aus Pyromellithsaure-dianhydrid und einer Vielfalt von Diaminen hergestellten Polyimide wurde eine gut definierte Abstufung der Stabilitat beobachtet. Die einfachsten und symmetrischsten Strukturen besaBen die hochste Warmestabilitat ; die schlechtesten Resultate wurden mit elektronegativen Kopplungsgruppen erzielt.

The molecular structure of poly(biphenyl dianhydride-p-phenylenediamine) polyimide thin films by infrared spectroscopy: Thickness dependence of structure in the nano- to micrometer range

“…Because the Imide IV transiphases in other polyimides, 27,32 we conclude that our films exhibit a thickness-independent chain tion moment is perpendicular to the imide ring plane (Fig. 2), 25 this mode must be inactive in packing. Second, Figure 4 shows that a near exact fit of the simulated C|C PDA band occurs for both normal incidence spectra for a ring planar to the substrate surface.…”

“…26 The diagnostic modes are located (see Fig. 1 25,27 The transition dipole directions of these bands are indicated in terms of the molecular coordinates shown in Figure 2. More complete band assignment information has been given by Boerio, and Ishida.…”

“…The spectral features observed are those expected from previous work. 25 As a basis for our detailed analyses we briefly review spectral assignments selected for those modes that are useful diagnostics of the chain structures. For reference, Figure 2 shows an isolated chain segment in the trans configuration with the chain axis at Ç 7.5Њ from the line connecting the C{N bonds of the paradianiline moiety.…”

“…More complete band assignment information has been given by Boerio, and Ishida. 25,27 Determination of Optical Function Spectra for BPDA-PDA from Free-Standing Films and from Isotropic Particulate Dispersions Normal incidence transmission spectra were used to determine the in-plane components of the film parallel to the stacking plane and be active. The figure shows that the n P KBr in (n)-based simulation (rrrrrr) fits the observed peak positions generally within a few cm 01 , while the simulated line widths are about 1 3 larger than observed.…”

Aromatic polyimides: Synthesis, characterization, and evaluation of electric strength

“…The influence of the chemical structure and the degree of imidization on the electric breakdown properties was tested on five structurally different polyimides [14][15][16] prepared in the lab ( Scheme 1 ) . To investigate the influence of the polymer molecular mass on the electric breakdown properties.…”