Electric-field-induced viscosity change of a nematic liquid crystal with gold nanoparticles.

The electro-rheological (ER) effect of a composite material consisting of a nematic liquid crystal (LC) and gold nanoparticles covered with mesogenic groups is discussed. The gold nanoparticles are covered by alkyl chains and liquid-crystalline compounds. The influences of the alkyl-chain length and the coverage by the alkyl chain and the mesogenic group on the miscibility of the nanoparticles with the LC are investigated by polarizing optical microscopy (POM). The presence of the gold nanoparticles in the nematic LC (5CB) leads to an enhanced ER response compared to that observed for 5CB. The prominent ER effect observed in this study is supported by the two mechanisms proposed, that is, the homogeneous and heterogeneous mechanisms. This study demonstrates the potential of a hybrid system consisting of an LC and gold nanoparticles to improve the ER effect.