Constructing High-Performance Dielectrics via Molecular and Phase Engineering in Dipolar Polymers

When one considers that outstanding dielectric polymers satisfy the developed requirements in the electronic and electrical industries, it is necessary to explore the structure–property relationship of all-organic polymer dielectrics. In this paper, two kinds of side-chain sulfonyl-containing dipolar polymers based on polyolefin main chains, poly{2,5-bis[(4-(methylsulfonyl)phenyl)oxycarbonyl]styrenes} (PBSO2) and poly{2,5-bis[(4-(methylsulfonyl)ethyl)oxycarbonyl]styrenes} (PESO2), were prepared via radical polymerization. The effect of the side-chain structure on the phase behavior, phase structure, dielectric property, and energy storage of dipolar polymers was investigated. The results showed that PBSO2 possessed a high glass transition temperature (Tg ≈ 195 °C) and formed the columnar nematic phase owing to the rigid side-chain structure. A dielectric constant of 20.8 (25 °C, 103 Hz) was obtained for the polymer PBSO2 due to the highly orientational polarization and the possible interfacial polarization between the amorphous phase and liquid crystalline phase, which is 18% higher than that of PESO2. However, PBSO2 exhibited a low breakdown strength because of the low band gap of ≈3.46 eV and brittleness of the film. In contrast, a low Tg of 78 °C and isotropic phase were found in the polymer PESO2. In addition, a discharge energy density of 6.2 J/m3 at 270 MV/m was achieved, which was attributed to the high dipole density. This study indicates that it is effective to improve the dielectric constant by introducing a liquid crystalline phase into a dipolar polymer, which offers a route for synthesizing high-performance dielectric polymers.