High-frequency low-dielectric-loss in linear-backbone-structured polyimides with ester groups and ether bonds

Polyimides have emerged as promising dielectric materials for communication equipment, owing to their excellent thermal stability and processability. Nonetheless, a pressing need remains to reduce the high-frequency dissipation factor ( D f ) of polyimides. Here, we synthesized various polyimides featuring linear backbone structures, finding that polyimides that incorporate a combination of ester groups and ether bonds exhibit low D f values of 0.0015-0.0024 at 10 GHz. Even in high humidity and temperature conditions they maintain low D f values of <0.005 at 10 GHz. To gain insight into the factors influencing this behavior, we conduct a comprehensive study involving aggregation structures and hygroscopic properties. Our findings highlight the pivotal role of high orientation and crystallinity in determining the high-frequency D f of polyimide films.