1. School of Molecular and Microbial Sciences, Australian Institute of Bioengineering and Nanotechnology, University of Queensland, Brisbane QLD 4072, Australia; Department of Polymer Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands; and Rhodia Recherches, Centre de Recherches d'Aubervilliers, 52, rue de la Haie Coq, 93308 Aubervilliers Cedex, France