Synthesis and characterization of new aromatic polyamides bearing crown ethers or their dipodal counterparts in the pendant structure.: I.: Benzo-12-crown-4 and ortho-bis(2-ethoxyethoxy)benzene

Two novel isoplithalic diacid-based monomers have been synthesized by inclusion in ring position 5 of a functionalized benzoylamine moiety. The functionalization includes a 12-crown-4 ether group fused with the benzene subunit and a dipodand substructure, formally a disubstitution of the benzene ring, with two sequences of ethyl-terminated ethylene oxide units, which represent the open-chain counterpart of the alicylic crown moiety. The polycondensation of the two diacids with five aromatic diamines yielded 10 new polyamides with crown or podand pendant substructures. The polyamides had previously been chemically characterized by NMR, IR, and elemental analysis. The polymers showed high glass transition temperatures of up to 349 degrees C, good thermal stability (T-d (onset), (N2) approximate to 400 degrees C), and improved solubility in organic solvents. The presence of acyclic or alicyclic oxyethylene sequences as crown ether or podand substructures and an additional amide side group per repeat unit made the polymers essentially amorphous and improved their water absorption ability in comparison with nonsubstituted polyamides. Water uptake values as high as 12% were observed at 65% relative humidity. All the polyamides showed a good film-forming ability, and the mechanical properties of these films are considered to be satisfactory for experimental aromatic polyamides. (c) 2006 Wiley Periodicals, Inc.