On the dynamic mechanical behavior of polyimides based on aromatic and alicyclic dianhydrides

A series of polyimides has been synthesized based on different dianhydrides and diamines. The microstructure of polyimide films has been analyzed by performing density measurements, X‐ray diffraction and UV‐visible spectrophotometry. The dynamic mechanical behavior was investigated according to both chemical and microstructural aspects. Thus, it was pointed out that the broadness of the β subglass transition is dependent not only on dianhydride flexibility but also on para‐ or meta‐diamine links. Such behavior is discussed in terms of intra‐charge transfer complex. On the contrary, the temperature location of the γ‐transition appears to be controlled by interchain packing. Based on a statistical approach, a correlation between microstructural data and gamma relaxation temperature is established.