A facile preparation of hyperbranched copper phthalocyanine microspheres and their wideband microwave absorption properties

Hyperbranched copper phthalocyanine (CuPc) with uniform spherical morphology has been firstly obtained by ethylene glycol solvothermal synthetic route. The highly dispersed spherical CuPc aggregates with a diameter of ~500 nm. X-ray diffraction indicated that the molecules were stacked into one-dimensional b-axis aggregate. In addition, the split Soret band together with the broadened and blue-shifted Q-bands in the optical spectra suggested the H (face-to-face) type of interactions in the arrangement of macrocycles in a dense-packed structure. Due to its good symmetrical structure and unique morphology, the hyperbranched spherical CuPc showed excellent broadband microwave absorption behaviors in a frequency of 2-18 GHz. Over an absorber of 5 mm thickness, an absorption bandwidth of 12 GHz corresponding to reflection loss below -10 dB can be obtained. The high value of microwave reflection about -50 dB at the frequency of 16.5 GHz also suggested that the hyperbranched spherical CuPc can be used as promising microwave absorbing materials.