It is an urgent issue to enhance the energy storage capacity of dielectric film capacitors for the miniaturization, lightweight and integration of electron devices under the premise of large-scale industrial...

How to achieve synergistic improvement of permittivity (εr) and breakdown strength (Eb) is a huge challenge for polymer dielectrics. Here, for the first time, the π‐conjugated comonomer (MHT) can simultaneously promote the εr and Eb of linear poly(methyl methacrylate) (PMMA) copolymers. The PMMA‐based random copolymer films (P(MMA‐co‐MHT)), block copolymer films (PMMA‐b‐PMHT), and PMMA‐based blend films were prepared to investigate the effects of sequential structure, phase separation structure, and modification method on dielectric and energy storage properties of PMMA‐based dielectric films. As a result, the random copolymer P(MMA‐co‐MHT) can achieve a maximum εr of 5.8 at 1 kHz owing to the enhanced orientation polarization and electron polarization. Because electron injection and charge transfer are limited by the strong electrostatic attraction of π‐conjugated benzophenanthrene group analyzed by the density functional theory (DFT), the discharge energy density value of P(MMA‐co‐PMHT) containing 1 mol% MHT units with the efficiency of 80% reaches 15.00 J cm−3 at 872 MV m−1, which is 165% higher than that of pure PMMA. This study provides a simple and effective way to fabricate the high performance of polymer dielectrics via copolymerization with the monomer of P‐type semi‐conductive polymer.

Developing new polymer dielectrics with superior dielectric and energy storage properties is urgent to meet the demand for electronic devices in the field of microminiaturization or harsh environments. In this paper, two dipolar glass polymers based on polynorbornene main chain and flexible/rigid cyano side chain were synthesized by ring opening metathesis polymerization method: polymer PCEMT with flexible side chains and polymer PCPMT with rigid side chains. The backbone is built from two rigid five-membered rings, which not only avoids the narrow band gap caused by π−π conjugation of traditional aromatic main chains, but also maintains high thermal stability and high glass transition temperature (T g ). The introduced polar cyano groups on the side chain gave high dielectric constants (ε r ) for both polymers, where the ε r of PCEMT and PCPMT reached 7.9 and 4.6 at room temperature and 1 kHz, respectively. Due to high polarization and high breakdown strength, the PCPMT obtains a maximum discharge energy density (U d ) of 4.47 J/cm 3 at room temperature, which is 1.61 and 1.57 times of biaxially oriented polypropylene and polyimide (Kapton). The supernal T g of 229 °C makes the energy storage performance of PCPMT almost unaffected at 100 °C. The charge−discharge efficiency (η) always keeps over 90% and an U d of 5.2 J/cm 3 at 480 MV/m is achieved, which is much better than Kapton (U d = 1.77 J/cm 3 , η = 42.5%) under the same conditions. This work provides a new idea for preparing the high-performance polymer dielectrics via introducing rigid polar side chains.

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