Block copolyetheresters with hard segments of poly(trimethylene 2,6-naphthalene dicarboxylate) and soft segments of poly(tetramethylene ether)glycol 2,6-naphthalene dicarboxylate were prepared by the melt polycondensation of dimethyl 2,6-naphthalene dicarboxylate (NDC), 1,3-propanediol (PD), and poly(tetramethylene ether)glycol (PTMEG) with molecular weights of 1000. The block copolyetheresters were characterized by H-1-NMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. The block copolyetheresters synthesized with NDC/PD/PTMEG were more heat resistant than those synthesized with dimethyl terephthalate/PD/PTMEG. The block copolyetheresters synthesized with NDC/PD/PTMEG showed stronger elastoplastic behavior than those synthesized with NDC/1,4-butanediol/ PTMEG. (C) 2003 Wiley Periodicals, Inc.