A. Linear Increase of Molecular Weight With M/I Ratio Controlled Polymerization of -Amino Acid-N-Carboxyanhydrides Jianjun Cheng, Department of Materials Science and Engineering, University of Illinois, Urbana, IL 61801 We discovered controlled ring-opening polymerization of -Amino Acid-N-Carboxyanhydrides (NCAs) mediated by N-TMS amines (JACS, 2008, 130, 12562; JACS, 2007, 129, 14114) Table. Glu-NCA Polymerization Initiated by Various N-TMS Amines Figure. Controlled Living Glu-NCA Polymerization Initiated by N-TMS Allylamine (1-TMS) A. Linear Increase of Molecular Weight With M/I Ratio Various N-TMS amines, such as benzylamine (2), morpholine (3), propargylamine (4), N-(aminoethylene)-5-norbornene-endo-2,3-dicarboximide (5), and mPEG2000 amine (6), representing primary (2) and secondary amines (3), amines containing functional groups that can be used for further reactions such as click chemistry (4) and ring-opening metathesis polymerization (5), and terminal amines of polymers (6), can initiate controlled Glu-NCA polymerization. PBLG MWs show linear correlation with the monomer/initiator ratio with remarkably small deviations from the expected MWs (Figure above), demonstrating N-TMS allylamine mediated controlled, living NCA polymerization.