Polyimide‐Polydimethylsiloxane Copolymers. Evaluation of the Thermal and Electrical Properties

Poly(dimethylsiloxane‐amic‐acid)s have been prepared starting from a fluorinated dianhydride, namely 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride, and a mixture of an aromatic diamine and bis(aminopropyl)‐oligodimethylsiloxane of controlled molecular weight, in different ratios. A solution imidization procedure was used to convert them quantitatively to the corresponding polyimides. The polymers, easily soluble both in polar (N‐methylpyrrolidone) and less polar (chloroform) solvents, were prepared for film‐forming by casting from solution. The thermal behavior in dependence on composition was evaluated by thermogravimetric analysis and differential scanning calorimetry. The kinetic processing of thermogravimetric data was carried out using the Flynn‐Wall‐Ozawa and Kissinger methods. Electrical insulating properties of some polymer films were evaluated on the basis of dielectric constant and dielectric loss tangent and their variation with frequency.

Keywords:

• polyimide‐polydimethylsiloxane copolymers
• good solubility
• thermal stability
• thermal degradation kinetics
• thin films
• dielectric constant

Acknowledgements

This research occurred in the framework of the Project CEEX –MATNANTECH 10/2005 for which the authors acknowledge financing authority.