1. Department of Polymer Science and Engineering, Kumoh National Institute of Technology, Kumi, Kyungbuk 730-701, Korea, Liquid Crystal Institute, Kent State University, Kent, Ohio 44242, Department of Chemistry, Gyeongsang National University, Chinju 660-701, Korea, Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784, Korea, and Department of Physics, Korea University, Chungnam 339-700, Korea