The DX centre
T.N. Morgan
Semiconductor Science and Technology
A general method for the controlled synthesis of polylactide in solution and from solid supports is presented. The evaluation of stannous(II) trifluoromethane sulfonate [Sn(OTf)2] and scandium(III) trifluoromethane sulfonate [Sc(OCTf)3] as catalysts for the ring-opening polymerization (ROP) of L-, D-, and L,D-lactide is described as a route to polylactide using mild and highly selective conditions. These triflate catalysts must be used in conjunction with a nucleophilic compound such as an alcohol that is the actual initiating species via the active metal alkoxide species. Consistent with this process, 1H NMR analysis revealed that the α-chain-end bears the ester from the initiating alcohol, and upon hydrolysis of the active metal alkoxide chain end, a ω-hydroxyl chain end was clearly detected. Polymers of predictable molecular weights and narrow polydispersities were obtained in high yields in accordance with a controlled polymerization process. The addition of base either as a solvent or additive significantly enhanced the polymerization rate with minimal loss to the polymerization control. The ROP of lactide isomers from an initiator, HO(CH2CH2O)3(CH2)11SH, self-assembled onto a gold surface using Sn(OTf)2 produced polylactide brushes under living conditions and provides the opportunity to prepare stereoregular or chiral surfaces by polymerization of enantiomerically pure monomers.
T.N. Morgan
Semiconductor Science and Technology
R.W. Gammon, E. Courtens, et al.
Physical Review B
M.A. Lutz, R.M. Feenstra, et al.
Surface Science
R. Ghez, J.S. Lew
Journal of Crystal Growth