Self-assembly of ferroferric oxide liquid-crystalline nanocomposites bearing cholesteryl mesogens and ionic groups

Abstract

ABSTRACT Magnetorheological fluids (MRFs) are promising smart materials that can respond to an external field. In order to obtain stable suspension and investigate the settlement law of these synthesised MRFs, polymerised ionic liquid crystalline (PILC) ferroferric oxide nanocomposites (Fe3O4@PILCs), the dispersed phase in MRFs, were obtained by self-assembly of magnetic Fe3O4 nanoparticles with PILCs. The structural properties, thermotropic liquid crystal characteristics, morphology and microscopic magnetic response characteristics were investigated in this study. Fe3O4@PILCs showed nematic liquid crystal behaviour, and the mesogenic phase range was affected by the content of cholesteryl-based LC mesogen containing carboxylic acid groups. Series of MRFs were prepared by the Fe3O4@PILCs with 5% particles mass fractions in different volume fractions. The settlement stability as well as the settlement laws was investigated comprehensively and systematically for these MRFs. The Fe3O4@PILC-based MRFs exhibited better sedimentation stability than the bare Fe3O4-based MRFs, indicating that the Fe3O4 particles self-assembled with PILCs could reduce the density of the dispersed phase and showed the good compatibility with silicone oil carrier fluid. The sedimentation velocity curves of the Fe3O4@PILC-based with different particle volume fractions were investigated by use of some relevant theoretical models, indicating that they were the most consistent with the Dick’s model.