The nature of dielectric losses in H‐Film

Based upon the high‐temperature solid‐state dielectric behavior of H‐Film and supporting evidence from infrared spectroscopy, heat capacity, thermal expansion, and dynamic mechanical measurements, it is concluded that the actual chemical structure of H‐Film is far more complex than previously expected. The very unusual thermal properties of this polymer, such as lack of a glass transition temperature, its extreme insolubility, and high dielectric losses above 250°C with only weakly corresponding mechanical losses, suggest that in addition to the pyromellitimide repeat unit, a significant part of the structure consists of amide groups, probably in the form of crosslinks.