Emeritus Professor of Physics
Liquid crystal polymers (LCP) share features of both polymers (good film forming and mechanical properties) and liquid crystals (LC – intermediate degrees of order between solid and liquid, and particularly optical, electro-optical and magneto-optical properties). In this class of materials, Prof. Schuele and I work primarily with comb-like polymers consisting of a polymer backbone. The side groups are composed of LC groups (mesogens) attached by methylene (carbon-hydrogen) chains which serve as spacers, thereby forming thermotropic LC mesophases (nematic, smectic, etc.). A knowledge of the molecular dynamics of various parts of these polymers is necessary to an understanding of their thermal behavior and to design materials for applications such as bistable optical devices. We employ dielectric relaxation methods as a function of frequency and temperature to study these dynamics, since the various dipole moments in the molecules act as probes of local molecular motions. As the LC head groups generally possess strong dipole moments, dielectric relaxation spectroscopy provides a direct method for studying the reorientational motion of these groups. Alignment of the LC head groups can be very useful in such studies and is also important to applications. This can be produced by electric or magnetic fields, or by other means such as flow.
Polymer stabilized liquid crystals represent another class of materials of current interest in which dielectric spectroscopy is yielding important information. These are formed from a mixture of conventional low-mass LC and other LC molecules containing polymerizable groups. After inducing long range orientation of the mixture between specially treated surfaces by the application of an electric field, photopolymerization produces networks. These consist of interconnected three dimensional anisotropic networks and of LC molecules which are not chemically connected to the network. Such systems offer interesting opportunities for exploring the behavior of LC molecules in anisotropic confinements and restricted geometries, as well as showing optical effects useful in device applications.
In the area of education my interests include developing multi-media materials for use in training undergraduate and graduate students in connection with activities of the Advanced Liquid Crystalline Optical Materials Science and Technology Center here at Case Western Reserve University. These involve text, image, audio, video, and CD-ROM based information, and will be designed for applications ranging from self-study to support materials for general lectures. An example module dealing with polymers and liquid crystals in the display industry is being prepared. In addition, Prof. McGervey and I sponsor and organize a Local Alliance Group of physics teachers from high school and college and of middle school science teachers which meets periodically during the year to share ideas, resource material and to provide encouragement.