1. School of Materials, The University of Manchester, Grosvenor Street, Manchester M1 7HS, U.K., Laboratoire de Thermodynamique des Solutions et des Polymères, Université Blaise Pascal / CNRS UMR 6003, 24, avenue des Landais, 63177 Aubière Cedex, France, Huntsman Polyurethanes, Everslaan 45, 3078 Everberg, Belgium, and Department of Chemical Engineering, Imperial College, Prince Consort Road, London SW7 2BY, U.K.