Copolymerization of fluorene-based main-chain benzoxazine and their high performance thermosets.

A series of fluorene-based benzoxazine copolymers were synthesized from the mixture of 9,9-bis(4-hydroxyphenyl)fluorene and bisphenol A, and 4,4′-diaminodiphenyloxide and paraformaldehyde. And the cured polybenzoxazine films derived from these copolymers were also obtained. Fourier transform infrared spectroscopy (FTIR) and hydrogen nuclear magnetic resonances confirmed the structure of these benzoxazines. Their molecular weight was estimated by gel permeation chromatography. The curing behavior of the precursors was monitored by FTIR and differential scanning calorimetry. Dynamic mechanical analysis and thermogravimetric analysis were performed to study the thermal properties of the cured polymers. The cured polybenzoxazines exhibit excellent heat resistance with glass transition temperatures ( T_g) of 286-317°C, good thermal stability along with the values of 5% weight loss temperatures ( T₅) over 340°C, and high char yield over 50% at 800°C. The mechanical properties of the cured polymers were also measured by bending tests. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]