The thermal behavior of poly(ethylene-co-2,2-bis[4-(ethylenoxy)-1,4-phenylene]propane terephthalate) (PET/BHEEBT) copolymers was investigated by thermogravimetric analysis and differential scanning calorimetry. A good thermal stability was found for all the samples. The thermal analysis carried out using DSC technique showed that the T-m of the copolymers decreased with increasing BHEEBT unit content, differently from T-g, which on the contrary increased. Wide-angle X-ray diffraction measurements permitted identifying the kind of crystalline structure of PET in all the semicrystalline samples. The multiple endotherms similar to PET were also evidenced in the PET/BHEEBT samples, due to melting and recrystallization processes. By applying the Hoffman-Weeks' method, the T(m)degrees of PET and its copolymers was derived. The isothermal crystallization kinetics was analyzed according to Avrami's treatment and values of the exponent n close to 3 were obtained, independently of T-c and composition. Moreover, the introduction of BHEEBT units was found to decrease PET crystallization rate. Lastly, the presence of a crystal-amorphous interphase was evidenced. (c) 2005 Wiley Periodicals, Inc.