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 3‐step reaction for using as the applications of low‐ k materials. The synthesized FBMI monomers are characterized by the 1 H, 13 C, 19 F 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 128–141°C and show the 5% weight loss temperatures ( T 5% ) of 235–293°C in nitrogen atmosphere. The higher heat resistance of self‐curing FBMI resin relative to FBMI‐homopolymer is due to its higher crosslinking density. The FBMI resins exhibit improved dielectric properties as compared with commercial bismaleimide (BMI) resins with the dielectric constants ( D k ) lower than 2.49, which is related to the low polarizability of the CF bond and the large free volume of CF 3 groups in the polymers. Besides, the flame retardancy of all these FBMI resins could be enhanced via the introduction of Br‐atom.