Studies of fluorine-containing bismaleimide resins. Part I: Synthesis and characteristics of model compounds

A series of fluorine-containing bismaleimide (FBMI) monomers are synthesized by a 2-step reaction for using as the applications of low-k materials. The synthesized FBMI monomers are characterized by the ¹H, ¹³C, ¹⁹F nuclear magnetic resonance (NMR) spectroscopy and element analysis. These FBMI monomers react with free radical initiator or self-cure to prepare FBMI-polymers. All the self-curing FBMI resins have the glass transition temperatures T _g in the range of 130–141°C and show the 5% weight loss temperatures T _5% of 280–322°C in nitrogen atmosphere. The higher heat resistance of self-curing FBMI resin relative to FBMI-homopolymer is due to its higher cross-linking density. The FBMI resins exhibit improved dielectric properties as compared with commercial bismaleimide (BMI) resins with the dielectric constants ? lower than 2.44 which is related to the low polarizability of the C-F bond and the large free volume of CF₃ groups in the polymers. Besides, the flame retardancy of all these FBMI resins could be enhanced via the introduction of Br-atom.