 |
Miles's Project Page |
 |
Teacher Intern: Heather Miles
Mentor:Krystyna R. Brzezinska
Department: MRL |
2004 Research Project: Polymerization of ã-Benzyl-L-glutamate-N-carboxyanhydride (GluNCA)
Initiated by Difunctional and Monofunctional Initiators. Kinetics Study.
Polypeptides are interesting polymers because their structural complexity
imparts these materials with specific biological functions. Side reactions that
occur during formation of the polypeptide segments have been a major limitation
in the synthesis. Our results demonstrated that amido-amidate nickelacycle end
groups can be incorporated onto 2,2-dimethyl-1,3-propanediamine, and the
resulting complexes can be used as difunctional initiator for polymerization of
ã-benzyl glutamate NCA (Glu NCA).
To prove difunctionality of the initiator we chose to compare the rates of
GluNCA polymerization using mono- and difunctional initiators. All rate
constants were measured at identical concentrations of the initiator = 1.2 10-3
M and [GluNCA] = 0.13 M. The monomer reactivity ratios were determined and
found to be kobs = (5.7±0.5) 10-4 sec-1 for difunctional initiator and kobs = (2.0±0.5) 10-4 sec-1
for monofunctional initiator. The polymerization rates were first-order in
monomer concentration to 3.5 half-lives, which indicated the lack of significant
chain termination events. Polymerization exhibited features characteristic of
living polymerizations. Polypeptide chain length scaled linearly with monomer
to initiator ratio while molecular weight distributions were low (Mw/Mn < 1.3).
Download Research Presentation as a PDF file
Return to the RET project list
