Circuit Simulation for the Dielectric Responses of the Composites of Copper Phthalocyanine Oligomers and Sulfonated Polyurethanes by Separating the Structural Elements

摘要

The copper phthalocyanine (CuPc) oligomer with high dielectric constant was synthesized by the solution method. The FT-IR and X-ray diffraction results revealed its chemical structure. The high dielectric constant of CuPc was proved to result from the free movement of charge carriers along the conjugated orbitals. The composites of CuPc and sulfonated polyurethane (PUI) were prepared and the contents of CuPc in the composites were varied from 10 to 50 wt %. The dielectric performance was greatly enhanced for the composite compared with that of average polymers. Different from the behaviors appeared in a common composite with conductive fillers, there is no percolation phenomenon observed in the CuPc/PUI composite, and the dielectric constants of CuPc/PUI composites decreased with the increase in the CuPc content, which is assumed to due to the strong electrostatic interactions between CuPc and PUI. Considering the many-body interactions within the bulk sample and the contact effect between the bulk sample and the metallic electrode, an equivalent circuit was established. to simulate the dielectric behaviors of the composites and computational curve fitting was done. The results were in good agreement, indicating that the dielectric responses of the composites come from both the extrinsic and the intrinsic contributions. The extrinsic was associated with the Maxwell-Wagner relaxation at the interface between the electrode and the bulk sample, and the intrinsic was associated with the huge dipoles provided by the mobile charges within the CuPc grains and the interaction among them in the bulk composites. A circuit model concerning the universal dielectric response was proposed in describing the intrinsic contribution, which quantitatively verified the strong interaction among the dipoles with the relaxation time, representing the aggregated structure of CuPc when its content was high in the composites.