1Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853 USA
2Department of Material Science and Engineering, Cornell University, Ithaca, NY 14853, USA
3Summer research student: Department of Chemistry, Simmons College, 300 The Fenway, Boston, MA 02115-5898, USA.
4Present address: Groupe BASF, Institut de Science et d'Ingénierie Supramoléculaires (ISIS)/Université Louis Pasteur (ULP), 8, allée Gaspard Monge, F-67083 Strasbourg, France.
5Department of Food Science, Cornell University, Ithaca, NY 14853, USA