New fluorinated xanthene-containing polybenzoxazoles with low dielectric constants

Abstract

Abstract A new bis( o -aminophenol), 9,9-bis(3-amino-4-hydroxyphenyl)xanthene (BAHPX), has been synthesized via nitration and reduction reaction from 9,9-bis(4-hydroxyphenyl)xanthene successively, and the corresponding fluorinated polybenzoxazoles (PBOs) containing xanthene cardo groups were prepared from BAHPX and five fluorine-containing aromatic dicarboxylic acids by one-step method. The resulting PBOs were almost completely amorphous and exhibited good thermal stability, with glass-transition temperatures of 295–323 °C, 10% weight loss temperatures of 560–582 °C and char yields more than 60% at 800 °C in nitrogen, respectively. These new PBOs exhibited improved solubility and were soluble in NMP at room temperature or at 60 °C, and could be cast into transparent, strong, free-standing films by solution casting with tensile strengths of 62–75 MPa, tensile moduli of 2.3–3.5 GPa, and elongations at break of 3.2–4.1%. In addition, these PBOs had low dielectric constants ranging from 2.52 to 2.68 (1 MHz), low moisture absorption in the range of 0.16–0.32%, and high transparency with an ultraviolet–visible absorption cut-off wavelength in the 334–352 nm range.