operate concurrently under high electric fields and elevated temperatures approaching or surpassing 150 °C. [2,4,8,[11][12][13] However, to date, the search for polymer dielectrics that provide appreciable energy densities at temperatures well above 100 °C has led to only marginal success. High temperature operation under high electric field is challenging for polymer dielectrics. For example, biaxially oriented polypropylene (BOPP), the state-of-the-art commercially available dielectric polymer used for energy storage, has a remarkable breakdown strength of ≈700 MV m −1 and ultralow loss, but can only operate continuously at temperatures up to 85 °C and for a short duration with significant derating at 105 °C. [14,15] Many heat resistant polymers have been designed and studied for high-temperature applications, but they are incapable of operating at an electric field similar to BOPP. [11,16,17] This is because their conjugated aromatic backbones that are able to withstand high temperature, built at the cost of largely reduced bandgaps, lead to high electrical conductivities and poor energy densities especially at elevated temperatures. Recent efforts for enhanced energy storage performance at high temperature via nanocomposites or coating modifications of polymer films, although encouraging, are prohibitively challenging for industrial-scale production due to requirements of (either) materials cost and (or) laborious multi-step synthesis and processing. [2,12,13,18,19] As a result, BOPP is still used today with cumbersome active cooling. The availability of flexible polymer dielectrics, capable of stable operation under ultrahigh electric field and elevated temperature is the limiting factor for high power density electrification and electronics.Due to hot carrier excitation, injection, and transport, assisted under thermal and electric extremes, polymers exhibit a nonlinear increase in electrical conduction, [20][21][22] leading to the reduction of the discharged energy density, largely increased energy loss and ultimately dielectric breakdown failure [23] . While the complexity of these processes makes the study of engineering conduction mechanism under critical electric fields far from fully understood, past studies revealed the dominant role of the bandgap in determining electrical conduction and intrinsic breakdown strength of the polymer dielectrics. [20,[24][25][26][27] However, careful evaluation of common high-temperature polymers reveals, unfortunately, an inverse Flexible dielectrics operable under simultaneous electric and thermal extremes are critical to advanced electronics for ultrahigh densities and/or harsh conditions. However, conventional high-performance polymer dielectrics generally have conjugated aromatic backbones, leading to limited bandgaps and hence high conduction loss and poor energy densities, especially at elevated temperatures. A polyoxafluoronorbornene is reported, which has a key design feature in that it is a polyolefin consisting of repeating units of fairly rigid fused bicycl...

The dielectric constant (ϵ) is a critical parameter utilized in the design of polymeric dielectrics for energy storage capacitors, microelectronic devices, and high-voltage insulations. However, agile discovery of polymer dielectrics with desirable ϵ remains a challenge, especially for high-energy, high-temperature applications. To aid accelerated polymer dielectrics discovery, we have developed a machine-learning (ML)-based model to instantly and accurately predict the frequency-dependent ϵ of polymers with the frequency range spanning 15 orders of magnitude. Our model is trained using a dataset of 1210 experimentally measured ϵ values at different frequencies, an advanced polymer fingerprinting scheme and the Gaussian process regression algorithm. The developed ML model is utilized to predict the ϵ of synthesizable 11,000 candidate polymers across the frequency range 60–1015 Hz, with the correct inverse ϵ vs. frequency trend recovered throughout. Furthermore, using ϵ and another previously studied key design property (glass transition temperature, Tg) as screening criteria, we propose five representative polymers with desired ϵ and Tg for capacitors and microelectronic applications. This work demonstrates the use of surrogate ML models to successfully and rapidly discover polymers satisfying single or multiple property requirements for specific applications.

A paradigm-shifting design strategy is demonstrated that unifies the treatment of electronic and conformational properties of polymer dielectrics for concurrent high electric field and elevated temperature harsh conditions.

The electronic structures of carbon nanotube/RuO2 core/shell nanocomposite (RuO2 thin layer coated multiwalled carbon nanotubes (MWNTs)) have been studied by X-ray absorption near-edge structures (XANES) at C K-edge, O K-edge, and Ru M5,4- and L3-edges. The variation in white-line features of the XANES at these edges supports strongly that RuO2 interacts with MWNTs through Ru−O−C bonding, which also results in charge redistribution between C 2p-derived states in MWNT and the conduction band in RuO2. Such chemical bonding is necessary to immobilize RuO2 on MWNT and ensures good conductivity of MWNT/RuO2 core/shell nanocomposite.