Optical characterization of a ferroelectric liquid crystalline polymer studied by time-resolved optical waveguide spectroscopy

The static structures and switching dynamics of a side chaia ferroelectric liquid crystalline polymer (PSiOFLC) were investigated by using time-resolved optical waveguide spectroecopy (TROWS). A good alignment of the mesogenic side chains was obtained by a shearing procedure. The liquid crystalline phases of PSiOFLC wore characterized by determining the dielectric tensor diagonals of PSiOFLC, in which the contribution of the main chain to the optical anisotropy could be neglected. The PSiOFLC layer in the S_A phase could be treated as a uniaxial refractive index ellipsoid which aligned parallel to the substrate plane with bookshelf structure. The PSiOFLC layer in the S_c. phaee under the large electric field was also considered ae a uniaxial ellipsoid model. The transient waveguide mode patterns of PSiOFLC were successfully obtained with a millisecond time resolution. During the reorientation, the emectic layer structure changed from bookshelf to chevron and then back to the bookshelf structure. The slowness of the switching time was attributed to a "polymer effect" in which the polymer backbones lying in the emectic layer plane act as a "hook" to restrict the motion of aide chains due to the binding of the mesogenic moieties to the polymer backbone, resulting in the increase of viscosity.