Poly(ethylene terephthalate), PET reacted with various glycols in the presence of titanium tetraisopropoxide as a catalyst. The glycolyzed PET was fractionated into two parts-soluble and insoluble in CHCl3-characterized and used as a raw material to synthesize copolyesters. The soluble part in the CHCl3 part was a mixture of monomers and oligomers, and no melting points were observed. On the other hand, in the insoluble part a melting point was determined. The glycolyzed PET and copoly(succinic anhydride/ethylene oxide), PES were condensed to produce copolymers. The synthesized copolyesters were amorphous and hydrolyzed enzymatically due to a decrease in the crystallinity.