Enhanced dielectric behavior in nanocomposites of polyurethane bonded with copper phthalocyanine oligomers

To increase the electric energy density of dielectric elastomers, high dielectric constant nanocomposites were developed by chemically bonding oligomers of copper phthalocyanine oligomers (CuPc), a high dielectric constant organic semiconductor, to polyurethane (PU). Transmission electron microscope (TEM) images revealed that the sizes of the CuPc particles in the nanocomposite of PU functionalized with 8.78 vol% of CuPc were in the range of 10–20 nm, much smaller than the sizes (250–600 nm) in PU blended with the same volume fraction of CuPc. At 100 Hz, the nanocomposite film exhibited a dielectric constant of 391, representing a more than 60-fold increase with respect to pure PU. The enhanced dielectric response in the nanocomposite makes it possible to induce a high electromechanical response. A strain of 17.7% and an elastic energy density of 0.927 J cm−3 were achieved under an electric field of 10 V μm−1.