1. Polymer Program Institute of Materials Science University of Connecticut Storrs CT 06269 USA
2. Department of Chemical and Biomolecular Engineering University of Connecticut Storrs CT 06269 USA
3. Magnetic Resonance Center Boston College Chestnut Hill MA 02467 USA
4. State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical Technology Beijing 100029 China
5. Department of Biomedical Engineering University of Connecticut Storrs CT 06269 USA