1. Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400, Department of Organic and Polymeric Materials, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152, Japan, and School of Polymer, Textile & Fiber Engineering, Georgia Institute of Technology, 801 Ferst Drive, Atlanta, Georgia 30332-0295