1. 1Research & Development Center, Toyo Tire & Rubber Co., Ltd. 5-7 Nishichujo, Ibaraki-shi, Osaka 567, Japan
2. 2Institute for Chemical Research, Kyoto University Gokasho, Uji-shi, Kyoto 611, Japan
3. 3Department of Polymer Science and Engineering, Kyoto Institute of Technology Matsugasaki, Sakyo-ku, Kyoto-shi, Kyoto 606, Japan