1. Department of Chemistry Northeast Normal University Changchun 130024 P. R. China
2. Key Laboratory of Polymer Ecomaterials Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun 130022 P. R. China
3. Department of Spinal Surgery The First Hospital of Jilin University Changchun 130021 P. R. China
4. Jilin Biomedical Polymers Engineering Laboratory Changchun 130022 P. R. China