Magnetorheological liquid-crystalline polymers with magnetic tetrachloroferrate ions based on polyvinyl chloride

Novel magnetic ionic polymers based on polyvinyl chloride ([PVCs][FeCl4]) with liquid-crystalline (LC) ordering were synthetised and characterised. The [PVCs][FeCl4] containing magnetic tetrachloroferrate ions were prepared with PVC, pyridyl LC monomers and FeCl3. Various devices and instruments were used to characterise the chemical structure, thermal behaviour, magnetic properties, and LC properties. The synthetised [PVCs][FeCl4] showed smectic LC phase and presented excellent thermal stability. Several magnetorheological (MR) fluids were prepared using [PVCs][FeCl4] as particles and silicone oil as carrier fluid. MR Effects and settlement stability were investigated. Under the condition of external magnetic field, the MR fluids showed Bingham flow characteristics, and the MR effect was enhanced with increasing FeCl4− content in the systems. Under the condition of magnetic field intensity of 80 kA/m and shear rate of 2.5 s−1, the magnetorheological efficiency of [PVCs][FeCl4] based MR fluids with particle concentration of 20% can reach up to 14.7. The excellent MR effect of [PVCs][FeCl4] was due to the strong coupling between the magnetic moment of the FeCl4− anion and the orientation of cationic LC primitive under the action of an applied magnetic field. Furthermore, the good settling stability of the MR fluids was due to the introduction of organic mesogens, PVC main-chains and the ionic components for the [PVCs][FeCl4] particles.