A set of new block copolyimides containing fluorenyl cardo moieties (FR) in the polyimide blocks and poly(ethylene oxide) (PEO) sequences has been prepared using the two-step method of polyimide synthesis. The combination of both moieties led to novel copolyimides with good solubility in a variety of solvents, which could easily be processed into films. Copolyimides with PEO content from 30 to 56 wt % were amorphous, showed good mechanical properties, and absorbed less water than other PEO-containing polyimides previously reported. Copolyimides with higher PEO content (60 and 65%) showed crystallinity and yielded soft films. All of the copolymers showed two glass transition temperatures, the first one around -25 degrees C attributed to the PEO segments, and the second one at much higher temperature, which corresponded to the polyimide domains. The thermal degradation occurred in two steps, the first one being associated with the degradation of the PEO segments and the second one with the generalized aromatic polyimide decomposition. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8170-8178, 2008