Thomas M. Leslie

Large Kerr effects in transparent encapsulated liquid crystals

The encapsulation of liquid crystals in a polymer matrix produces a material with interesting and potentially useful optical properties. The earliest efforts generated a dispersed phase whose dimensions were comparable to optical wavelengths and therefore afforded materials which were highly scattering. These materials have already been found useful for display applications. We have found that when these materials are fabricated so that the dimensions of the dispersed phase are substantially smaller than the incident radiation wavelengths, the material is far less scattering. dc Kerr measurements on these liquid‐crystal composites yield quite large values, ranging as high as 30 000 times CS2 This activity is shown to be a strong function of the liquid‐crystal loading and the temperature.

Temperature calibration of a power compensation DSC on cooling

Abstract The temperature calibration of a Perkin-Elmer DSC7 has been performed on cooling using the isotropic to nematic or cholesteric transitions of thermally stable liquid crystals. Correspondence has been established between the actual temperature and the temperature indicated by the instrument at different cooling rates for most heating rate calibrations used in practice. It has been shown that the indicated temperature at any heating rate calibration up to 20°C min−1, and cooling rates up to 20°C min−1, does not differ from the actual temperature by more than 2°C. Therefore, uncorrected results can be used at the heating and cooling rates mentioned. Greater differences were observed at higher heating and cooling rates.

Development of Polymeric Nonlinear Optical Material

Abstract The molecular structural characteristics which give rise to large optical nonlinearities have been delineated. This has been accomplished by several key steps and has led to the development of a structural algorithm for the design of β molecules with high susceptibilities. High activity molecular units have been covalently attached to form polymers which can contain up to 100% of the NLO moiety, and the resulting molecular optical properties have been characterized. The second order molecular susceptibility was found to be undiminished by properly designed covalent bonding to form a polymer, and spectral characteristics were found to closely follow that of the NLO unit.

Development Of Polymeric Nonlinear Optical Materials

Commercial interest in nonlinear optical (NLO) materials is driven by the development of fiber optics, laser diodes, and high speed computing. In communications, as well as in information processing, the direction of future technology points unmistakably towards optical systems. Active materials for optical modulation, routing, and amplification are in high demand for this technology. Currently available materials for NLO applications lack many of the critical requirements for true industrial implementation. Therefore, significant programs for the development of improved NLO materials have blossomed throughout the world. Organics have been suggested as improved materials for a variety of applications ranging from conducting polymers to superconductors. For NLO applications, there is a solid foundation of basic science which clearly defines intrinsic advantages of these materials in comparison to those which are currently in use. In addition to basic material constants, organics offer the opportunity to apply molecular level science to engineer materials through application of several principles of design. In this paper, these design concepts will be highlighted in an attempt to define an industrial approach to this materials problem.

Characterization of polymeric nonlinear optical materials

The development of organic nonlinear optical materials requires the accurate measurement of its nonlinear optical and electrooptical properties. These measurements provide a guide to the synthesis and fabrication of new nonlinear organic materials with improved properties. A new technique for the electrooptical characterization of thin polymeric films is presented. This technique is used to measure the linear electrooptical Pockels effect in poled MNA/PMMA guest host glassy polymers. These results are compared to x(2) values derived from second harmonic generation studies. D. C. Kerr effect results are reported for a novel sol gel glass/PMMA composite material containing MNA. These results probe the relative mobility of MNA in PMMA at room temperature and elevated temperatures. x(3) values of several organic liquids are also measured by third harmonic generation studies in air. These values are compared with those derived from measurements in vacuum and good agreement is found between the two techniques.

Exploratory Studies on Novel Liquid Crystal Acrylates

Abstract Three new liquid crystalline monomers were synthesized and polymerized. The backbone was either acrylate or methacrylate, and polar groups with a chiral center were incorporated into the mesogens. Two monomers displayed a smectic C* phase below room temperature, while the third one was a plastic lc. The homopolymers and copolymers had lc phases, smectic C* or smectic A, between 40 and 80°C.