In situ observation of smectic layer reorientation during the switching of a ferroelectric liquid crystal

A thin plastic cell containing the ferroelectric liquid crystal ZLI3654 (4 μm) was placed edge-on to a pin-hole collimated horizontal X-ray beam. In this way, the smectic layers were brought into register. Subsequently, triangular voltage waves with various peak (V_p) values were applied across the cell and diffraction photos were obtained during the application of the alternating voltage. Up to V_p = ± 30 V, no significant movements in the initial tilted orientation of the smectic layers with respect to the surfaces (chevrons) could be observed. During the application of V_p = ± 32 V an increasing fraction of the smectic layers changed their initial tilt angle with respect to the cell surfaces to make larger tilt angles. At a slightly higher voltage, the layers became upright (bookshelf structure). Upon removing the voltage and short circuiting the cell, the quasi-bookshelf structure was sustained. The new method described here can be used in combination with a fast detector for time resolved experiments.