Studies on switching mechanism of ferroelectric polymer liquid crystals by time-resolved optical waveguide spectroscopy

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1.Development of time-resolved optical waveguide spectroscopy (TROWS)The switching times of most ferroelectric liquid crystals range from micro-to milli-second, which means one must develop an instrument with a time-resolution faster than microsecond. The first step of this research was conserned with this issue, and the TROWS we made could detect transient optical waveguide mode patterns under the switching every a few tens nanoseconds.2.Dynamics of flow molecular weight nematic liquid crystalsThe new technique using TROWS was applied firstly to the study of low molecular weight nematic liquid crystals. The molecular motion under external electric field was analyzed by a multi-layr approximation, showing that the angle distribution and its time dependence between two stable states of homeotropic and parallel orientations.3.Studies on transient structures of a ferroelectric liquid crystalThe internal structures of a ferroeletric liquid crystal under a static high-electric feild and und … More er the inversion of its polarity, were investigated.From the analysis of waveguide modes, we found a transient bending motion of the smectic layrs such as bookshelf*chevron*bookshelf, and it was revealed that on the way of switching, the molecules in upper and lower halves between the electrodes take place an unti-symmetrical cone motion synchronized with the bending of chevron structure.4.Switching mechanism of ferroelectric polymer liquid crystalsFerroelectric polymer liquid crtstals were investigated on the basis of the knowledge obtained for low molecular weight ones. The transient waveguide patterns clearly showed the existence of bending motion of smectic layrs as well as low molecular weight liquid crystals. Since the polymer main chains locate between smectic layrs, they have little effect on the rotational motion of the mesogenic side chains, which perform a coherent motion among layrs under alternating electric field. These cooperative motions enable the side chains to switch their orientation with a high speed as fast as low molecular liquid crystals. Less