1. Maurice Morton Institute and Department of Polymer Science, The University of Akron, Akron, Ohio 44325-3909; National Key Laboratory of Polymer Physics and Chemistry, Chinese Academy of Sciences, Changchun, Jilin, 130022, P. R. China; Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323; and Department of Engineering Materials, University of Sheffield, Sheffield S1 3JD, UK