Liquid-crystalline behavior and magnetorheological effect of PVC-based ionic polymers with tetrachloroferrate anions

Abstract

• Ionic liquid-crystalline (LC) polymers with FeCl 4 − were synthesized by PVC and FeCl 3 . • The magnetorheological (MR) effect and LC behavior were investigated. • The MR fluids were fabricated by the ionic polymer and silicone oil. • The MR effect was caused by a synergistic effect between the LC orientation and rearrangement of FeCl 4 − . Ionic polymers based on tetrachloroferrate anions (FeCl 4 − ) have become one of the attractive functional materials due to their magnetic property. Series of polyvinyl chloride (PVC)-based ionic polymers ([PBCs][FeCl 4 ]) containing tetrachloroferrate anions were prepared by self-assembly using PVC, cholesteric pyridine-3,5-dicarbonate, 4,4 -bipyridine and FeCl 3 ·6H 2 O, and their liquid-crystalline (LC) behavior and magnetorheological (MR) effect were investigated in this study. The chemical structure, thermal properties and LC behavior were characterized by various equipment and instruments. The magnetic field response behavior, MR effect, and sedimentation stability were investigated by various technical methods. The [PBCs][FeCl 4 ] showed smectic A phase on heating and cooling cycles. The magnetorheological fluids (MRFs) were fabricated by the [PBCs][FeCl 4 ] polymers as suspended particles and silicone oil as carrier liquids, which presented a Bingham flow characteristics under an external magnetic field. For these [PBCs][FeCl 4 ]-based MRFs, both shear stress and magnetorheological effects increased with the increase of magnetic field strength, and it exhibited a maximum MR efficiency of 15.3 at 1.23 s −1 of shear rate under 80 kA/m of magnetic field strength. The MR effect of the [PBCs][FeCl 4 ]-based fluids was originated from a synergistic effect between the LC orientation of the mesogens and rearrangement of the FeCl 4 − anions when an external magnetic field was applied.