Dynamics of a Ferroelectric Liquid Crystal with a Naphthalene Ring during Electric-Field-Induced Switching Studied by Time-Resolved Infrared Spectroscopy Combined with Two-Dimensional Correlation Spectroscopy

摘要

The dynamics of a ferroelectric liquid crystal with a naphthalene ring (FLC-3) during the electric-field-induced switching between two surface-stabilized ferroelectric liquid crystal states were investigated by time-resolved infrared (IR) spectroscopy combined with two-dimensional (2D) correlation spectroscopy. Time-resolved IR spectra of FLC-3 in a planar-aligned cell were measured as a function of the polarization angle range from 0° to 180° under a rectangular electric field of ±40 V with a 5 kHz frequency in the smectic-C~(*) (Sm-C~(*)) phase at 137℃. From these spectra we explore details about the reorientation process of the alkyl chains, the core, and the large C=O dipole moments of FLC-3 at all the delay times. The 2D correlation spectroscopy was applied to the polarization-angle-dependent spectra for different delay times and to the time-resolved spectra at certain polarization angles to reveal the relative orientation of the C=O groups and the core moiety during the electric-field-induced switching. It was found from the present study that the relative orientation of the C=O groups and the core remains unchanged during the initial period of the reorientation, while it is reversed at a certain moment and then kept unchanged again. Moreover, the alkyl chains, C=O groups, and core moieties posses different dynamics during the fast course of electric-field-induced switching by analyzing time-resolved spectra.