1. National Institute of Materials and Chemical Research, MITI, Higashi 1‐1, Tsukuba, lbaraki 305, Japan
2. Department of Industrial Chemistry, Faculty of Science and Technology, Science University of Tokyo, 2641 Yamazaki, Noda, Chiba 278, Japan
3. Institute of Colloid and Interface Science, Science University of Tokyo, 1‐3 Kagurazaka, Shinjuku, Tokyo 162, Japan