Synthesis, curing behavior, and thermal properties of fluorene-based benzoxazine-endcapped copoly(ether ketone ketone)s
A series of fluorene-based benzoxazine-endcapped copoly(ether ketone ketone)s (co-PEKKs) were successfully synthesized, in which the co-PEKKs were prepared with different molar ratios of 2,7-dihydroxy-9-fluorenone to bisphenol-A. The obtained phenol-ended co-PEKKs reacted with formaldehyde and n-butylamine to yield the benzoxazine-endcapped co-PEKKs (B-PEKKs). The structure of these oligomers was studied by Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy, and the molecular mass of these phenol-ended co-PEKKs was detected by gel permeation chromatography. The thermal behaviors of these B-PEKKs were determined by differential scanning calorimetry. In addition, the thermal and dynamic mechanical properties of the polymer films were investigated by thermogravimetric analysis and dynamic mechanical analysis. The results indicate that the incorporation of co-PEKKs within the benzoxazine backbone considerably improves the toughness of the fluorene-containing polybenzoxazines without much sacrifice of their thermal properties. Furthermore, as the content of 2,7-dihydroxy-9-fluorenone increases, the T5 values decrease, while the Tg values and char yields of the prepared polymers increase to reach their highest values at 256 °C and 64 %, respectively.