1. Department of Polymer Chemistry Graduate School of Engineering Kyoto University Katsura Nishikyo‐ku Kyoto 615‐8510 Japan
2. Department of Applied Chemistry Graduate School of Engineering Hiroshima University 1‐4‐1, Kagamiyama Higashi‐Hiroshima Hiroshima 739‐8527 Japan
3. Department of Maxillofacial Surgery Graduate School of Medical and Dental Sciences Tokyo Medical and Dental University 1‐5‐45, Yushima Bunkyo‐ku Tokyo 113‐8510 Japan
4. Bioresource Research Center Tokyo Medical and Dental University 1‐5‐45, Yushima Bunkyo‐ku Tokyo 113‐8510 Japan
5. Materials Sciences Research Center Japan Atomic Energy Agency 2–4 Shirakata‐Shirane, Tokai Naka‐gun Ibaraki 319‐1195 Japan