3-p-Hydroxyphenyl-6-p-hydroxybeiizylidene cyclopentapyrazoline (III) and 3-vanillyl-7-vanillylidene cyclopentapyrazoline (IV) were used as new starting materials for preparing new unsaturated polyesters. The polyesters were prepared by reacting (III) or (IV) with adipoyl, sebacoyl, isophthaloyl, and terephthaloyl dichlorides utilizing the interfacial polycondensation technique. The polyester samples have been characterized by elemental and spectral analyses. The polyesters have inherent viscosities of 0.55-0.97 dL/g. All the polyesters are semicrystalline and most of them are partially soluble in most common organic solvents but freely soluble in concentrated sulfuric acid. Their glass transition temperatures (T-g) range from 103.34 to 208.81 degrees C, and the temperatures of 10% weight loss as high as 190 to 260 degrees C in air, indicating that these aromatic polyesters have high T-g and excellent thermal stability. Doping with iodine dramatically raised the conductivity and produced dark brown colored semiconductive polymers with a maximum conductivity in the order of 3.1 x 10(-7) Omega(-1) cm(-1). (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 3727-3736, 2010