Polyimides, nonaromatic

Inherent viscosities (Tiinh) of the poly(amic acid)s were as low as 0.08-0.23, however, they formed flexible and tough films. In the IR spectra of nonaromatic polyimides, characteristic imide absorptions at 1767 cm"1 (asym C=0 str.) and 1699-1703 cm 1 (sym C=0 str.) were observed, and the absorptions of amic acid groups have practically disappeared. 

Film refractive index n was determined using an Abbe refractometer at room temperature. The dielectric constant e of the material at a frequency near 1 MHz is evaluated roughly from the refractive index to be e=l.ln2.[7] These results are listed in Table 1. Optically estimated e s of the nonaromatic polyimides were approximately 2.6, whereas those of semi-aromatic and aromatic polyimides were around 2.8 and 3.1, respectively.[6] The birefringence An (optical anisotropy) of sample films was evaluated by means of ellipsometry. All the nonaromatic polyimides examined in this study possessed small birefringence below 10"4. 

Table 1. Synthesis and the properties of nonaromatic polyimide films/...

Figure 4. WAXD patterns of the nonaromatic polyimide films.

All of the highly aromatic polymers are resistant, relative to the nonaromatic polymers, to irradiation with either electron beam or y-rays. When irradiated in a vacuum many of these polymers are very stable and can show no change in physical properties even after high beam doses. For example, Kapton and Vespel aromatic polyimides have been shown to have resistance to both y-rays and electron beams up to doses of 100 MGy of irradiation [184]. In the presence of oxygen, the physical properties of the aromatic polymers can be dramatically changed. For example, an aromatic polysulfone showed no change in the flexural strength after irradiation with y-rays to 6 MGy, in vacuo. On the other hand, when the irradiation is carried out in the... 

Matsumoto Toshihiko. Nonaromatic polyimides derived from cycloaliphatic monomers. Macromolecules. 32 no. 15 (1999) 4933-4939. 

Matsumoto T. Nonaromatic Polyimides Derived from Cycloaliphatic Monomers. Macromolecules 1999 32 4933-4939. 

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