Polyesters PEs containing high content of fluorene units in their backbones were synthesized from 9,9-diarene-substituted fluorene diols (1) and fluorene-based diacid chlorides (2) by high temperature polycondensation at 185 degrees C in diphenyl ether. The molecular weights of the polyesters PE1-PE5 were in a range of M-w 25,000-165,000. The polyesters displayed their high thermostability: the glass transition temperatures (T-g) by differential scanning calorimetry analysis ranged from 109 to 217 degrees C, while the 10% weight loss temperatures (T-d10) measured by thermogravimetric analysis were over 400 degrees C in nitrogen and 395 degrees C in air. The polyesters had good solubility in most common organic solvents such as chloroform and toluene and gave tough, transparent and flexible cast films. The transmittance of the films was over 80% in the wavelength range from 450 to 700 nm in any PEs. The PEs exhibited high refractive index values around 1.65, while they had very low degree of birefringence. (C) 2008 Wiley Periodicals, Inc.