Poly(ether ester) elastomers (PEEs) were synthesized in which dimethyl terephthalate (DMT) was the primary diester compound in the hard segment (H/S) and dimethyl 2,6-naphthalene dicarboxylate (NDC), which has a more rigid aromatic chemical structure than DMT, was the secondary diester in the H/S. The block PEEs with poly(tetramethylene terephthalate) (PTMT) and/or poly(tetramethylene 2,6-naphthalate) (PTMN) as the H/S and poly(tetramethylene ether glycol terephthalate) (PTMEGT) as the soft segment (S/S) were synthesized through transesterification and polycondensation of DMT, NDC, 1,4-butanediol (BD), and poly(tetramethylene ether) glycol (PTMEG) of molecular weight 1000. The melting temperature and heat of fusion of the PEEs decreased with increasing NDC content up to an NDC content of 44.4% in the H/S, but increased on further increase of the NDC content. In addition, the higher the fraction of NDC in the H/S, the higher the glass transition temperature of the copolymer. X-ray diffraction analysis revealed that the crystallinity of the sample decreases as the NDC content in the H/S is increased relative to that of DMT. Increasing the PTMN content in the H/S reduced the effect of UV photodegradation on the elongation at break. The results show that the introduction of the NDC component into the H/S as a secondary diester compound improves the UV resistance of the resulting PEE. (C) 2003 Wiley Periodicals, Inc.