MICROSECOND TIME-RESOLVED INFRARED STUDY OF THE ELECTRIC-FIELD-INDUCED REORIENTATION OF NEMATIC LIQUID-CRYSTALS

Microsecond time-resolved infrared spectroscopy has been used to study the time course of the electric-field-induced reorientation of a nematic liquid crystal, 4-n-pentyl-4'-cyanobiphenyl (5CB) and its partially deuterated analogue (5CB-d2). The temporal responses to a pulsed electric field were markedly distinct between the infrared bands due to the pentyl group and those due to the cyanobiphenyl group. It is likely that, in the course of reorientation, the pentyl part and the cyanobiphenyl part can move distinctly through the internal rotation around the C(biphenyl)-C(pentyl) bond. It was also found that the motion of the pentyl part precedes that of the cyanobiphenyl part at the early stage of reorientation.