OPTICAL CHARACTERIZATION OF A FERROELECTRIC LIQUID-CRYSTALLINE POLYMER STUDIED BY TIME-RESOLVED OPTICAL WAVE-GUIDE SPECTROSCOPY

The static structures and switching dynamics of a side chain ferroelec tric liquid crystalline polymer (PSiOFLC) were investigated by using t ime-resolved optical waveguide spectroscopy (TROWS). A good alignment of the mesogenic side chains was obtained by a shearing procedure. The liquid crystalline phases of PSiOFLC were characterized by determinin g the dielectric tensor diagonals of PSiOFLC, in which the contributio n of the main chain to the optical anisotropy could be neglected. The PSiOFLC layer in the SA phase could be treated as a uniaxial refractiv e index ellipsoid which aligned parallel to the substrate plane with b ookshelf structure. The PSiOFLC layer in the S-c phase under the larg e electric field was also considered as a uniaxial ellipsoid model. Th e transient waveguide mode patterns of PSiOFLC were successfully obtai ned with a millisecond time resolution. During the reorientation, the smectic layer structure changed from bookshelf to chevron and then bac k to the bookshelf structure. The slowness of the switching time was a ttributed to a ''polymer effect'' in which the polymer backbones lying in the smectic layer plane act as a ''hook'' to restrict the motion o f side chains due to the binding of the mesogenic moieties to the poly mer backbone, resulting in the increase of viscosity.