Time-resolved infrared spectroscopic study of the switching dynamics of a surface-stabilized ferroelectric liquid crystal.
The orientation dynamics of a ferroelec. liq. crystal with a naphthalene ring (FLC-3) during the elec.-field-induced switching between two surface-stabilized states was investigated by means of time-resolved Fourier-transform IR spectroscopy. Time-resolved IR spectra of the planar-aligned cell of FLC-3 were measured as a function of the polarization angle ranging from 0 Deg to 180 Deg under a rectangular elec. field +-40 V with a 5-kHz repetition rate in the smectic-C* (Sm-C*) phase at 137 DegC. From these spectra details about the mutual arrangement of different mol. segments at all the delay times in the Sm-C* phase were derived. It was found that the C=O group in the core moiety exhibits a dynamical behavior different from that in the chiral moiety during the elec.-field-induced switching between the two surface-stabilized states. The most important finding in the present study is that during the elec.-field-induced switching the FLC mol. not only rotates around the layer normal, but also revolves around its own long axis. Furthermore, time-resolved IR spectroscopy revealed that each group in the core moiety passes almost simultaneously through the projection of the layer normal in the cell window during the dynamic switching.
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