1. Department of Chemistry, McGill University, Montreal, Quebec, Canada H3A 2K6
2. Current address: Rutgers, The State University of New Jersey, Department of Mechanics and Materials Science, Piscataway, NJ 08854
3. Institute of Polymer Science, University of Akron, Akron, OH 44325
4. Current address: Department of Polymer Science, University of Southern Mississippi, Hattiesburg, MS 39406-0076