Jun Shen1, Yoshio Okamoto1,2. 1. Polymer Materials Research Center, Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, College of Materials Science and Chemical Engineering, Harbin Engineering University , Harbin 150001, People's Republic of China. 2. Graduate School of Engineering, Nagoya University , Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan.