A series of thermotropic liquid crystalline copolyesters based on p-acetoxybenzoic acid, 2,7-diacetoxynaphthalene, terephthalic acid and polyethylene 2,6-naphthalate were prepared via melt transesterification. Their thermotropic liquid crystalline behavior was studied by visual observation on the hot stage of a polarized light microscope. The dependence of the crystallizability and melting temperature of the copolyesters on the 2,7-diace-toxynaphthalene content was examined by x-ray diffraction and differential scanning calorimetry. A blend sample was prepared by physically mixing 40% thermotropic copolyester and 60% polyethylene terephthalate and the phase-separated charackter of the copolyester and PET in the blend was proved by TOT and dynamic mechanical measurements. The SEM micrographs of the as-spun fibers of the blend show separation of the two phases. The highly oriented macromolecules and the fibril alignment of the mesomorphic copolyester in the blend has also been revealed after the dissolution of the PET phase in a solvent.