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Copoly(ether-imide)s formed by the reaction of an aromatic dianhydride (BPDA), an aromatic diamine (ODA), and various aliphatic diamines (PEO-2000, PPO-2000, RT-1000, pTHF-1700 have been obtained. These copolymers underwent phase segregation processes, as confirmed by small-angle X-ray scattering (SAXS), when they were thermally treated. Gas permeabilities of these materials depended on the phase separation. Thus, a linear relationship between gas permeability and increasing percentage and size of the domains of the segregated phase has been obtained. The differences in the degree of segregation have been examined for the different aliphatic diamines used in the synthesis of the copolymers. The effect of polarity, length, and structure of the chain were examined in terms of permeability for the gases O 2 , N 2 , CO 2 , and CH 4 . It has been shown that long aliphatic chains with adequate polarity and the ability to interact with and enhance the condensation of a certain gas give better materials. Improved selectivities, approaching the Robeson limit, were seen as a consequence of the thermal treatment. Also, an interesting reverse selectivity has been observed for the mixture CH 4 /N 2 , probably due to a combined effect of a specific interaction and an increase in solubility of CH 4 in the soft segregated portions of the copolymer.

This paper reports the synthesis and characterization of a new rigid diamine monomer, having a spiro carbon moiety and an adamantane bulky group in its structure; namely spiro-(adamantane-2,9′(2',7'-diamino)-fluorene) (SADAF). After its synthesis, using a straightforward methodology, a novel family of aromatic polyimides (PIs) and polyamides (PAs) has been attained by reaction of SADAF with three aromatic dianhydrides and two diacid chlorides, respectively. Two of the polyimides were obtained through the formation of the corresponding polyamic acid and subsequent thermal cycloimidization, whereas the other one, the polyimide from SADAF and 2,2bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), could be synthesized by chemical imidization from the polyamic precursor. Regarding polyamides, two new ones, made from SADAF and isophthaloyl chloride (IPC) and the diacid chloride of 2,2bis(4-carboxyphenyl)hexafluoropropane (6FC) could be obtained. All the polymers showed high Tg, above 350 ºC, and excellent thermal resistance, with onset degradation temperatures higher than 450 ºC. Polymers formed by the combination of SADAF with 6FDA and 6FC were prepared as dense films with good mechanical properties and their permselectivity properties were measured.