The mechanical, thermal, electrical and moisture absorption properties of a series of fluorinated, highly rod-like polyimides and copolyimides are reported. Copolymerization with appropriate flexibilizing comonomers resulted in improved elongations versus those of the highly rod-like homopolymers while maintaining, to a large extent,the other desirable properties of the backbone. These materials are considered prime candidates for interlayer dielectric due to their excellent combination of properties.