The present work deals with the synthesis of thermally stable polymers that contain phenylthiourea, sulfone and azo group in the backbone from bisphenol and diacid chlorides. The bisphenol containing phenylthiourea and azo groups was synthesized via three steps. In the first step, 4,4'-bis(thiourea) diphenyl sulfone (BTDS) was obtained from 4,4'- diaminodiphenyl sulfone and ammonium thiocyanate. The second step involved the diazodisation reaction of 4-aminophenol. The third step in the preparation of the monomer was the coupling of bisthiourea (BTDS) with the diazonium chloride in the presence of an alkali which resulted in 4,4'-bis(p-hydroxyphenyl azo thiourea)diphenyl sulfone (HP-ATDS). The final step was the synthesis of polyesters by polycondensation reaction of this monomer with various acid chlorides (both aromatic and aliphatic). The polymers were characterized by solution viscosity, UV-Vis, FT-IR,'H-NMR and TGA. Solubility of the polymers was also tested with different solvents, which is an important parameter for the processablity of the polymer. The synthesis and characterization of the monomer and polymers is discussed herein