High- k Polymer Nanocomposites Filled with Hyperbranched Phthalocyanine-Coated BaTiO₃ for High-Temperature and Elevated Field Applications

Two sets of thermal stable nanocomposites were fabricated by using engineering plastics poly(ether sulfone) (PES) as a matrix and phthalocyanine molecules (CuPc) or hyperbranched phthalocyanine (HCuPc)-coated barium titanate (BT) nanoparticles as fillers for high electric field and high-temperature dielectric applications. By side-by-side comparison, the hyperbranched coating is finely addressed for enhancing the dielectric response and breakdown strength of the composites. Specifically, BT-HCuPc/PES exhibits 40% lower dielectric loss and about 110% larger breakdown strength than BT-CuPc/PES. The addition of hyperbranched phthalocyanine may enhance the compatibility and dispersion of the ceramic fillers in the polymer matrix and reduces the charge carrier between the filler and matrix. Meanwhile, high dielectric constant, high breakdown, and low dielectric loss are well-maintained in the composites filled with hyperbranched phthalocyanine-modified BT from room temperature to 150 °C. The discharged energy density of the composites (20 vol % BT-HCuPc/PES) can reach 2.0 J/cm³ at 300 MV/m, about 166% of that of the polymer matrix (1.2 J/cm³). Our findings on hyperbranched coating structure could be applicable to other ceramic-polymer composites to enhance their dielectric response.