Ferroelectric liquid crystals for second order nonlinear optics

Main-chain ferroelectric liquid crystal polymers (FLCPs) and oligomers are of interest as precursors to free standing glassy fibers with the FLCP stat ic structure. in particular, a supermolecular structure where the polar axi s is oriented normal to the fiber axis may be of utility for frequency mixi ng applications. We report herein the synthesis of just such a main-chain F LCP wherein the disperse red NLO chromophore is oriented preferentially nor mal to the fiber axis. The new polymer has MW approximate to 40 000 by cali brated gel permeation chromatography, representing a degree of polymerisati on of the 'side-by-side dimer' monomers of about 30 units. The phase sequen ce exhibited by this material (1-125 degrees-SmC*-85 degrees-glass) is usef ul for achieving the desired goal. Attempts to pull fibers from the SmC* ph ase were unsuccessful, But, nice free standing fibers were easily obtained from the isotropic melt by simple insertion and rapid removal of the closed end of a melting point capillary. Examination of 4 mu m fibers by polarise d light microscopy showed that the transition moment of the dye is preferen tially oriented normal to the fiber axis, and that the fast axis of the bir efringent fibers is along the fiber axis. These results suggest that the de sired supermolecular structure has been achieved.