All-organic ArPTU/PEI composite dielectric films with high-temperature resistance and high energy-storage density

All-organic dielectric materials require high performance in applications such as transportation, microelectronics, and aerospace power systems. In this work, aromatic polythiourea (ArPTU) was synthesized via a one-step method. A series of polymer composite films were prepared using ArPTU and polyetherimide (PEI) as raw materials. The experimental results showed that the composite films have better dielectric properties than the pure PEI films. Taking the blend membrane with an ArPTU mass fraction of 2% as an example, the composite films have good dielectric properties (ϵ_r = 3.58, tan δ = 0.007), high energy density (5.34 J cm⁻³ at an E_b = 580 MV m⁻¹), and a charge-discharge efficiency of 85% at 150 °C. At 25 °C, the maximum U_e was 5.75 J cm⁻³, and the efficiency could be maintained above 97%. It was speculated that the strong polarity of ArPTU and good compatibility with PEI were the reasons for its performance improvement. The ArPTU/PEI composite films demonstrated excellent comprehensive performances, combining the advantages of both ArPTU and PEI and have potential in a wide range of applications in the field of high-temperature media.