1. 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
We discovered the first living, controlled ring-opening polymerization of -Amino Acid-N-Carboxyanhydrides mediated by hexamethyldisilazane (HMDS) through a TMS carbamate end group.
Table. Glu-NCA Polymerization Initiated by HMDS
Figure. Controlled Living Glu-NCA Polymerization Initiated by HMDS
A. Linear Increase of Molecular Weight With M/I Ratio
aDEA = diethylamine; TBD = triazabicyclodecene bM (M/I) = Glu-NCA monomer (monomer/amine initiatro ratio); cConversion of monomer was quantified using FTIR by measuring NCA anhydride absorption band at 1790 cm-1; d(obtained from Penczek Ed. Models of Biopolymers by Ring Opening Polymerization)
HMDS has remarkable control of polymerization at nearly any selected monomer/initiator (M/I) ratio (Table, entry 1-6). The MWs of the resulting poly(gamma-benzyl-L-glutamate) (PBLG) show less than 35% of deviations from expected MWs. In comparison, conventional amine mediated Glu-NCA polymerization resulted in elevated PBLG MWs by a few orders of magnitude (entry 7-9).
PBLG MWs have a linear correlation to the monomer conversions and show remarkably small deviations from the expected MWs (Figure above), demonstrating HMDS mediated NCA living polymerization.