POLY 276 |
| Ring-opening polymerizations of α-amino acid N-carboxyanhydrides (NCAs) initiated with amines typically form polypeptides with uncontrolled molecular weights and broad molecular weight distributions. However, we found that hexamethyldisilazane (HMDS) mediated controlled NCA polymerizations and gave polypeptides with predictable molecular weights and narrow molecular weight distributions. Using MS, NMR and FT-IR, we demonstrated that the initiation step involved the cleavage of the N-Si bond of HMDS and the formation of a trimethylsilyl-carbamate (TMS-CBM) terminal group. Polypeptide chains propagated through the migration of TMS of the TMS-CBM end group to the incoming monomer and formed a new TMS-CBM terminal group. This organosilicon reagent mediated NCA polymerization offers a metal-free strategy for the convenient synthesis of homo- or block-polypeptides with predictable molecular weights and narrow molecular weight distributions. |
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Functional Nanomaterials from New Polymer Synthetic Methodologies
2:00 PM-5:50 PM, Monday, April 7, 2008 Hilton New Orleans Riverside -- Grand Salon 7/10, Oral
Division of Polymer Chemistry |