Effect of a temperature threshold on the electrorheological performance of ionic liquid crystal polyanilines

Abstract

A series of ionic liquid crystal polyanilines (ILCPs) electrorheological (ER) compounds were synthesized by use of polyaniline, naphthalene disulfonic acid and pyridinyl-containing mesogen. The chemical structure, thermal property, morphology, liquid-crystalline behavior, dielectric property and ER effect of the ILCPs-based ER fluids were characterized by use of various experimental techniques. The synthesized ILCPs displayed nematic liquid-crystalline phase, and the different mesogens played a determinant role in the liquid crystal behavior. The experimental results about dielectric property of the ILCPs suggested that both dielectric constant and dielectric loss increase with raising the temperature, showing a sudden change around glass-transition temperature. The ILCPs-based ER fluids contained an integrated character of liquid crystal, poly(ionic liquid) and polyaniline-base ER suspensions. These characteristics had strong dependence on operating temperature, and a temperature threshold was observed on the ER performance. The shear stress of the ER fluids increased abnormally near glass-transition temperature, which was due to the synergetic effect between the mesogenic orientation and the stretched polyaniline droplets induced by the electric field.