Triphenylphosphine oxide‐based bismaleimide and poly(bismaleimide): Synthesis, characterization, and properties

A novel phosphorus‐containing bismaleimide, 3,3′‐bis(maleimidophenyl)phenylphosphine oxide (BMPPPO), was synthesized from triphenylphosphine oxide. This bismaleimide exhibited good solubility in common organic solvents, such as methylethylketone, methylisobutylketone, dichloromethane, chloroform, tetrahydrofuran, acetone, methanol, ethanol, and hot toluene. A low melting point (Tm = 148 °C), a relatively low polymerization temperature (Tp = 214 °C), and a wide processing window (Tp − Tm = 66 °C) were also obtained for BMPPPO. This implies better processing capability. In contrast to most known phosphorus‐containing polymers, the incorporation of BMPPPO into poly(bismaleimide) enhanced the polymer glass‐transition temperature. Thermal stability at temperatures over 550 °C and char yields in the high‐temperature region over 700 °C were also improved. As a result, the flame‐retardant properties of the poly(bismaleimide)s were improved.