Magnetic and electrically conductive polyurethane composites with high content of two functional fillers base on "Root" inspired microstructure

The incorporation of functional fillers into polymer matrix endows composites with functionality, and filler content is an important factor that affects the performance and functionality of composites. In traditional pro-cessing methods, excessive filler usually deteriorates the continuity of polymer matrix, leading to composite developing crack or failing to support itself. Hence, the filler content cannot be usually maximized. Not to mention, the incorporation of two functional fillers with large quantity to achieve multi-functionalities. In this work, branched polyurethane (PU) dendrites with large aspect ratio and interpenetrating entangled structure are used to capture functional fillers. By introducing carbon nanotubes (CNTs) and carbonyl iron particles (CIPs) onto these "root" inspired dendritic PU, the resultant PU/CIPs/CNTs composite with PU:CNTs:CIPs weight ratio at 1:0.3:7 demonstrates excellent electrical conductivity of up to 5.2 S/cm, ferrimagnetic property >181.2 emu/g and favorable flexibility. The satisfactory conductivity endows composite the capacity to generate heat as a bias voltage applied according to Joule's law, and saturate temperature of 138.9 degrees C is developed under 3 V-voltage. Extensive magnetic responses are observed due to the extremely high ferrimagnetism. In combination with conductive property and flexibility, fascinating applications such as magnetic field sensor, magnetic controlled heating and switch are demonstrated, revealing wide promising application prospects of composites especially in flexible multifunctional electronics.