Design of reactive linear polyphosphazene to improve the dielectric properties and fire safety of bismaleimide composites

[Display omitted] •Dual network interpenetration strategy significantly improves impact toughness.•Exceptional fire shielding performances, ∼32.8 % reduction in total heat release.•48.4% decrease in total smoke production and LOI of 34.5% are achieved.•The optimized composite material has a dielectric constant as low as 2.67. The high-frequency transmission of 5th-Generation Mobile Communication Technology (5G) and more integrated mobile terminals pose a challenge to the safety and dielectric properties of existing electronic packaging materials. This work innovatively designs a linear polyphosphazene compound (PABN) with benzonitrile as the reactive side group. The prepared bismaleimide (BMI)/PABN is an excellent dielectric composite material, breaking the technical barrier of balancing fire safety and dielectric performance. With only 1 wt% PABN, the UL94 rating of BMI composite reaches V0, and the impact strength increases by 48.5 %, demonstrating excellent fire safety and toughness. Specifically, the dielectric constant (Dk) of the composite containing 4 wt% PABN is as low as 2.67, far meeting the requirements of 5G. In addition, the glass transition temperature (Tg) of all BMI/PABN composites is around 290 °C, and the initial decomposition temperature exceeds 400 °C, indicating potential applications in the integration and miniaturization of microelectronic devices.