Self-assembly, liquid crystalline behavior and electrorheological performance of phthalocyanine-contaning polysiloxanes

Abstract

Series of phthalocyanine-based ionic liquid-crystalline polysiloxanes (ILCPs) were self-assembled by bromo-polysiloxanes and zinc tetraaminophthalocyanine, and their chemical structure, thermal and liquid-crystalline (LC) behavior were characterized by various experimental techniques. The ILCPs exhibited hexagonal columnar phase and SmA phase. The effects of ionic phthalocyanine content and LC phase on the dielectric properties including dielectric constant and dielectric loss were investigated, which was closely related to their electrorheological (ER) effect. The ILCPs-based ER fluids (ERFs) were prepared by the ILCPs and silicone oil, and the ER performance was investigated at controlled test conditions. The ER effect increased with the increase of ionic phthalocyanine moieties for these ERFs. Furthermore, the ER efficiency of the ERFs at 330 K was much higher than that at 300 K at the constant conditions. The real-time response experiments of the ERFs was performed by switching alternately turned on or off the electric field, illustrating a synergetic rearrangement and orientation of the LC mesogens and the ionic phthalocyanine moieties along the direction of the electric field. Moreover, the ERFs showed good sedimentation property due to good compatibility between ILCPs’ polysiloxane matrix and the polysiloxane-based silicon oil.