Side‐Chain‐Type High Dielectric‐Constant Dipolar Polyimides with Temperature Resistance

Innovative dielectric materials with high-temperature resistance and outstanding dielectric properties have attracted tremendous attention in advanced electronical fields. Polyimide(PI) is considered a promising candidate for the modern electronic industry due to its excellent dielectric properties and comprehensive properties. However, the limited-adjustable range of dielectric constant and the difficulty to obtain a high dielectric constant restrict the application of PI as high dielectric materials. Herein, a novel diamine monomer (2,2'-bis((methylsulfonyl)methyl)-[1,1'-biphenyl]-4,4'-diamine (BSBPA)) containing a rigid biphenyl structure and high dipolar sulfonyl pendant groups is designed for high dielectric polyimides. The rigid biphenyl and polar sulfonyl pendant groups can reasonably optimize the molecular structure and orientational polarization of polyimides to improve their dielectric properties and thermal properties. Moreover, the effect of different bridge linkages on the dielectric properties is studied by using the different dianhydrides. Thus, the PI-BSBPA films especially the DSDA-BSBPA film (DSDA: 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride) achieve great thermal properties (T5%d of 377 °C and Tg of 358 °C) and excellent dielectric properties (6.95 at 1 kHz) along with high discharged energy density of 5.25 J cm-3 and charge-discharge efficiency of 90%. The collaborative control of main-chain and side-chain engineering is effective to endow the polyimides with high-temperature tolerance and high dielectric performance.