Block copolymers of poly(ethylene terephthalate) (PET) and a thermotropic liquid crystalline polyester have been synthesized by high temperature solution polycondensation. The influence of the reaction time on thermal behavior of the block copolymers has been determined by Differential Scanning Calorimetry (DSC). Block copolymers were also characterized by Carbon 13 Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA).