Microstructure and dielectric properties of P(VDF-TrFE-CFE) with partially grafted copper phthalocyanine oligomer

A new class of nanocomposites in which the high dielectric constant copper phthalocyanine oligomer (o-CuPc) was partially grafted to the poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)), a relaxor ferroelectric polymer, was developed. The new approach developed allowed for higher degree of grafting of o-CuPc to the polymer backbone and resulted in a nanocomposite [P(VDF-TrFE-CFE)-g-CuPc/CuPc] with o-CuPc inclusion size at about 60-100 nm. Compared with simple blend of the terpolymer and o-CuPc, a lower dielectric loss and higher breakdown field were achieved in the grafted nanocomposite which can be attributed to a more uniform distribution of o-CuPc particles in the polymer matrix as well as much reduced inclusion size. Moreover, the dielectric constant of the grafted nanocomposite at frequencies above 1 kHz is much higher than that of the simple blend, indicating an increased interface effect such as the exchange coupling which can enhance the dielectric response, as suggested recently by Li.(28) It is also interesting to note that at high frequencies (similar to 1 MHz), in addition to the improved dielectric constant, the grafted nanocomposite also exhibits a much lower dielectric loss than the matrix.