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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. [ABSTRACT FROM AUTHOR]

A flexible polymer nanocomposite has been developed via introducing Nd-doped BaTiO3 nanoparticles into the poly(vinylidene fluoride). This nanocomposite delivers a discharged energy density up to 12.5 J/cm3 under an electric field of 420 kV/mm with only a small loading of 1 vol.% Nd-BaTiO3. High discharged energy density, mechanical flexibility, light weight, ease fabrication and low cost makes it attractive for advanced microelectronics and electrical power systems. Our results demonstrate that ceramics with giant dielectric permittivity as viable fillers for polymer nanocomposite dielectrics with higher energy density.

[Display omitted] • An intrinsic high– k polyimide with rigid backbone and polar side groups was reported. • STP-PI presented high permittivity (5.2 ∼ 6.0) and excellent thermal stability. • At 200 °C, STP-PI delivered a discharge energy density of 3.68 J cm-3. • The OTFTs based on STP–PI showed a low threshold voltage and high mobility value. High–dielectric–constant (high– k) polymers are highly desirable for high energy density capacitors and low–voltage organic thin-film transistors (OTFTs). However, conventional high– k polymers suffer from low temperature resistance or crystalline state, hampering their applications in electronic devices in general environments. Herein, by accurate monomer design and mild polycondensation, we synthesize a new polyimide (STP–PI) featuring amorphous state, intrinsic high– k , very high thermal stability, and self-standing properties. Having polar side groups and rigid twisty backbones, the STP–PI exhibits both high and stable permittivity (5.2 ∼ 6.0 from 1 MHz to 100 Hz) and excellent thermal stability (T d5% > 450 °C and T g > 300 °C), superior to its counterpart without the polar side group. When applied for energy storage, STP–PI delivers a discharged energy density of 3.68 J cm−3 with discharge efficiency of 84% at 350 MV m−1 even at 200 °C, which makes a record among the state–of–the–art performance of instinct polymer dielectrics. When applied in low-voltage OTFTs as the dielectric layers, the devices show a low threshold voltage of −0.30 V and mobility value of 4.03 cm2 V−1 s−1. The design strategy paves a way of making high– k polyimides for high temperature energy storage and electronic applications. [ABSTRACT FROM AUTHOR]