A series of polymerized ionic liquid crystals (PILCs) bearing fluorinated cholesteryl mesogens were synthesized in this work, which include polymerized imidazolium bromides (PIBs) and polymerized imidazolium hexafluorophosphates (PIHs). The PIBs were synthesized using alkyl bromine-containing polysiloxanes and 1-butyl-1H-imidazole, and the PIHs were synthesized by anion metathesis reaction using the corresponding PIBs and KPF₆. The chemical structures, liquid crystalline (LC) properties, and electrorheological (ER) effect of these PILCs were characterized by use of various experimental techniques. All the PILCs showed smectic A mesophase on heating and cooling cycles. The smectic layer structure of these PILCs are originated from the rigid fluorinated cholesteryl mesogens and the flexible moieties in the LC phase, but the ion pairs (imidazolium cations–PF₆⁻, Im⁺–PF₆⁻; or imidazolium cations–Br⁻, Im⁺–Br⁻) can disperse in the polysiloxane matrix and expand the d-spacing in the smectic layers. The PIHs show lower T_g and T_i than the corresponding precursor PIBs, which is due to the larger ion volume of Im⁺–PF₆⁻ for PIHs than that of Im⁺–Br⁻ for PIBs. A series of 40 V% ER fluids were prepared by mixing the PILCs with polydimethylsiloxane (PDMS), and the ER behaviors were studied. All the PILC/PDMS fluids showed ER effect, and the PIH/PDMS fluids show a little greater ER effect than the PIB/PDMS fluids. The PILC droplets in the ER fluids become deformed owing to both the orientation of fluorinated cholesteryl mesogens and the suppression of ionic migration when a DC electric field was applied, resulting in the occurrence of ER effect. Copyright © 2015 John Wiley & Sons, Ltd.

A series of main-chain liquid-crystalline polymers (LCPs) with pendant sulfonic acid groups have been synthesized by use of biphenyl-4,4′-diol, 6,7-dihydroxynaphthalene-2-sulfonic acid, and bis(4-(chlorocarbonyl)phenyl) decanedioate in a one-step esterification reaction. Emeraldine base form of polyaniline (PAN) is doped by the synthesized sulfonic acid-containing LCPs to obtain PAN–LCP ionomers. A series of electrorheological (ER) fluids are prepared using the synthesized PAN–LCP ionomers and silicone oil. The chemical structure, liquid-crystalline behavior, dielectric property of LCPs, and PAN–LCP ionomers, and ER effect of the ER fluids are characterized by use of various experimental techniques. The synthesized sulfonic acid-containing LCPs and PAN–LCP ionomers display nematic mesophase. The PAN–LCP ionomers show a slight elevation of glass transition temperatures and decrease of enthalpy changes of nematic–isotropic phase transition compared with corresponding sulfonic acid-containing LCPs. The relative permittivity of the PAN–LCP ionomers is much higher than that of the corresponding sulfonic acid-containing LCPs. The ER effect of the PAN–LCP ionomer dispersions is better than PAN dispersions, suggesting a synergistic reaction should be occurred among liquid crystalline component, and PAN part under electric fields. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3395–3403, 2013