Synthesis of Fluorinated Polybenzoxazoles with Low Dielectric Constants

Two fluorinated aromatic bis(o-aminophenol)s, 1,1-bis(3'-amino-4'-hydroxyphenyl)-1-(3'-trifluoromethylphenyl)-2,2,2-trifluoroethane (6FAP) and 1,1-bis(3'-amino-4'-hydroxyphenyl)-1-(3',5'-ditrifluoromethylphenyl)-2,2,2-trifluoroethane (9FAP) were synthesized, which were allowed to polycondense with aromatic diacyl chlorides to afford the fluorinated aromatic polybenzoxazoles (PBOs) via a conventional two-step procedure in which the low-temperature solution polycondensation process was first performed to yield poly(o-hydroxyamide)s (PHAs) followed by the thermal cyclodehydration to give the PBOs. Experimental results indicated that the PHAs had inherent viscosities in the range of 0.29-0.68 dL/g, showing excellent solubility in organic solvents. The PHAs could be thermally cyclodehydrated into the corresponding PBOs at 260-370 degrees C. The obtained PBOs exhibited enhanced glass-transition temperature but decreased solubility with respect to the PHAs. The PBOs showed glass-transition temperatures in the range of 315-337 degrees C and excellent thermal stabilities with 5% original weight-loss temperatures (T-5) of >513 degrees C. Additionally, the PBO films had average refractive index of 1.5298-1.5656, birefringence of 0.0051-0.0092, and low dielectric constants of 2.57-2.70. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4668-4680, 2010