Polyimide–polydimethylsiloxane copolymers containing nitrile groups

A novel series of nitrile-containing polyimide–polydimethylsiloxane copolymers was prepared by polycondensation reaction of 4,4′-oxydiphthalic anhydride with a mixture of an aromatic diamine, namely 2,6-bis(3-aminophenoxy)benzonitrile, and bis(aminopropyl)oligodimethylsiloxane of controlled molecular weight, in different ratios. The polymers were easily soluble in polar organic solvents, such as N-methylpyrrolidone, N,N-dimethylformamide as well as in less polar solvents such as chloroform, and can be cast from solution into thin flexible films. The inherent viscosity was in the range of 0.43–0.55 dL/g. The polymers showed good thermal stability, the decomposition temperature being above 430 °C. They exhibited a glass transition temperature in the range of 149–219 °C, with reasonable interval between glass transition temperature and decomposition temperature. The surface morphology was investigated by scanning electron microscopy. The water dynamic contact angles were measured by tensiometric method. The free surface energy was evaluated based on Owens and Wendt equation. A composite film based on a polyimide–polydimethylsiloxane copolymer and pyrite ash powder has been prepared and its nanoactuation has been investigated.