A series of rigid aromatic polyesters containing substituted oligophenyls was prepared. Aliphatic and aromatic side groups were used to increase the solubility. New oligophenyldiols were synthesized by coupling aromatic Grignard reagents with aromatic halides, using palladium complexes as catalysts. The polyesters were prepared by melt polycondensation and characterized by viscosimetry, thermal analysis, and dynamic mechanical analysis. The temperature dependence of the intrinsic viscosity, in the range 30-85-degrees-C, was sensitive to the type and position of the side groups. Polyesters with aromatic substituents were stable up to 400-degrees-C. The glass transition temperatures of the polyesters with aromatic side groups were in the range 150-250-degrees-C. Dynamic mechanical analysis showed that in the cases where aromatic substituents were used to increase solubility, the obtained polymers appear to have useful mechanical properties at high temperatures. The glass transitions appeared in the range 150-220-degrees-C, while a plateau modulus in the range of 10(8) Pa was obtained at high temperatures (up to 350-degrees-C).