1. Polyurethane Research Laboratory, Tosoh Corporation, 1-8, Kasumi, Yokkaichi, Mie 510-8540, Japan
2. Department of Advanced Materials Science, School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 227-8561, Japan
3. Institute of Materials Structure Science, High Energy Accelerator Research Organization, Ibaraki 305-0801, Japan