Sue J. Mecham

Synthesis and Characterization of Segmented Polyimide-Polyorganosiloxane Copolymers

Polyimide-polydimethylsiloxane block or segmented copolymers are reviewed with respect to synthesis, characterization, structure-property relationships and other special characteristics. The siloxane-modified imides have developed into important materials over the past 10 years. Although some thermal and thermooxidative stability is lost through introduction of the siloxane segment, a number of improvements are also observed, in processibility, toughness, flexibility, adhesion and membrane performance, to mention a few. The chemistry involves first preparing an organo-functional siloxane oligomer of a few thousand molecular weight, by ring-opening equilibration processes in the presence of an end blocker to produce either aminopropyl or anhydride end-groups. The resulting oligomers are then usually reacted with the two imide-forming monomers to generate “randomly segmented copolymers”. If the siloxane block lengths are designed to exceed even 1000\( \overline M n, \) a microphase separation allows for the generation of two glass-transition temperatures and other desirable multiphase bulk properties, which are compositionally dependent. In addition, the hydrophobic nature of the siloxane microphase influences the surface properties, often in desirable ways, useful for aerospace and microelectronics, and these features are discussed in this review.