Synthesis and properties of modified polyimides containing multiple side methyl and biphenyl structures

With the rapid development of 5 G technology and microelectronics, there is an urgent demand to design and develop modified polyimide films with low dielectric constant as flexible matrix materials. In this work, a diamine containing multiple side methyl and biphenyl groups was synthesized by aromatic nucleophilicsubstitution reaction and oxidation-reduction reaction, respectively. Furthermore, this monomer was used to polymerize with four different commercially available dianhydrides (ODPA, BTDA, BPDA, and PMDA) to produce a class of polyimides (PI 3a similar to 3d). The structures of the diamine and its PIs are characterized, and the relationship between the structure and properties of the obtained PI films is investigated. These modified PIs are easy to cast into films and have low dielectric constants and water absorption. Their dielectric constants and dielectric losses are in the range of 2.66-2.91 and 0.00579-0.00677 at 1 MHz, respectively. Meanwhile, these PIs also maintains good thermal stability, with glass transition temperatures (Tg) higher than 284 degrees C and 10% weight loss temperatures in the range of 496-505 degrees C at N2.