1. The Polymer Centre and the Department of Chemistry, University of Sheffield, Brook Hill, Sheffield S3 7HF, UK; Department of Chemistry, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, UK; The SRS, CLRC, Daresbury Laboratory, Warrington WA4 4AD, UK; and School of Physics and Chemistry, Lancaster University, Lancaster LA1 4YA, UK