Temperature-Resistant Intrinsic High Dielectric Constant Polyimides: More Flexibility of the Dipoles, Larger Permittivity of the Materials

Abstract

High dielectric constant polymers have been widely studied and concerned in modern industry, and the induction of polar groups has been confirmed to be effective for high permittivity. However, the way of connection of polar groups with the polymer backbone and the mechanism of their effect on the dielectric properties are unclear and rarely reported. In this study, three polyimides (C0-SPI, C1-SPI, and C2-SPI) with the same rigid backbone and different linking groups to the dipoles were designed and synthesized. With their rigid structure, all of the polyimides show excellent thermal stability. With the increase in the flexibility of linking groups, the dielectric constant of C0-SPI, C1-SPI, and C2-SPI enhanced in turn, showing values of 5.6, 6.0, and 6.5 at 100 Hz, respectively. Further studies have shown that the flexibility of polar groups affected the dipole polarization, which was positively related to the dielectric constant. Based on their high permittivity and high temperature resistance, the polyimides exhibited outstanding energy storage capacity even at 200 °C. This discovery reveals the behavior of the dipoles in polymers, providing an effective strategy for the design of high dielectric constant materials.

Constructing Novel High-Performance Dipolar Glass Polymer Dielectrics by Polar Rigid/Flexible Side Chains

“…The reason for this difference is that the side-chain rigidity of PCPMT is large, and the two dipoles on the structural unit are in relative immobilization, thus leading to a relatively low polarizability of the dipoles. In contrast, the side chain of PCEMT has only one benzene ring, the steric hindrance effect is smaller than that of PCPMT, and the side chain is also easier to rotate, which is conducive to the orientation polarization of the dipole, so the ε r of PCEMT is higher than that of PCPMT . As the frequency of the alternating electric field increases from 10 3 to 10 7 Hz, the ε r of PCPMT and PCEMT decreases from 4.6 and 7.9 to 4.2 and 5.8, respectively, which is mainly derived from the failure of the dipole movement speed to keep up with the frequency change of the alternating electric field …”

“…In contrast, the side chain of PCEMT has only one benzene ring, the steric hindrance effect is smaller than that of PCPMT, and the side chain is also easier to rotate, which is conducive to the orientation polarization of the dipole, so the ε r of PCEMT is higher than that of PCPMT. 43 As the frequency of the alternating electric field increases from 10 3 to 10 7 Hz, the ε r of PCPMT and PCEMT decreases from 4.6 and 7.9 to 4.2 and 5.8, respectively, which is mainly derived from the failure of the dipole movement speed to keep up with the frequency change of the alternating electric field. 36 Figure 6b exhibits the dielectric loss (tan δ) of polymer PCPMT and PCEMT films as a function of frequency at room temperature.…”

Research progress of intrinsic polymer dielectrics with high permittivity

“…Since we cannot observe the movement ability of molecular chains from a macro perspective, to further understand the mechanism of the effect of the connection mode between polar groups and polymeric backbone on dielectric properties, Zheng et al. [119] designed and synthesised three PIs, which named C0‐SPI, C1‐SPI, and C2‐SPI respectively, with the same rigid skeleton and different dipole connection groups (Figure 25). All PIs had rigid structures and exhibited good thermal stability.…”

Exploration of Breakdown Strength Decrease and Mitigation of Ultrathin Polypropylene

“…Some high-temperature dielectrics are still being investigated in research laboratories despite holding promise for more exceptional dielectric properties and high-temperature ratings. Their challenges, such as their dielectric strength, dielectric loss, and high-quality film processing, remain [ 13 , 14 , 15 , 16 , 17 ]. In addition, some researchers have attempted to increase the energy density of BOPP by loading high-permittivity particles onto the outer surface of BOPP film via plasma-assisted solution coating, magnetron sputtering, or corona treatment [ 18 , 19 , 20 ].…”