Use of carbohydrates as initiators for lactone ring-opening polymerization
Our laboratory discovered that, by lipase-catalysis, carbohydrates function as initiators that are regioselectively attached to the carboxyl terminus of propagating chains (Bisht et al, 1998). As an example, a,b-ethylglucopyranoside (EGP) was used as a multifunctional monosaccharide initiator for PPL-catalyzed e-CL ring-opening polymerizations. For an e-CL/EGP ratio of 7:1, in the absence of solvent, a product resulted that had an Mn and Mw/Mn of 2 200 g/mol and 1.3, respectively. Structural analysis by 2-D NMR techniques showed that the reaction was highly regiospecific. In other words, oligo(e-CL) chains formed were attached by an ester group to the primary hydroxyl moiety of EGP. Subsequently, lipase PS-30 catalyzed the selective acrylation of the w-oligo(CL) hydroxyl terminus giving a macromer for free-radical polymerization. Alternatively, acetylation of the w-oligo(CL) hydroxyl terminus resulted in a macroinitiator for lactide ring-opening polymerization. This gave a multi-arm heteroblock copolymer with spatially organized oligo(CL) and oligo(lactide) chain segments.
Scheme 6: αβ-Ethyl glucopyranoside (EGP) initiated ring-opening polymerization of ε-caprolactone and trimethylene carbonate.
Scheme 7. Chemoenzymatic route to spatially defined heteroblock copolymers comprised of oligo(CL) and oligo(lactide) arms.
- Kumar, A.; Gross, R. A.; Wang, Y.; Hillmyer, M. A.; “Recognition by Lipases w-Hydroxyl Macroinitiators for Diblock Copolymer Synthesis” of Macromolecules; 35(20); 7606-7611, (2002).(PDF)
- K. S. Bisht, F. Deng, R. A. Gross, D. L. Kaplan and G. Swift, “Ethyl Glucoside as a Multifunctional Initiator for Enzyme-Catalyzed regioselective Lactone Ring-opening Polymerization” J. Am. Chem. Soc., Vol. 120, 1363-1367 (1998).(PDF)
- K. S. Bisht, R. A. Gross and A. L. Cholli, “Enzymatic Polymerization of Poly(-CL) Containing an Ethyl Glucopyranoside Head Group: An NMR Study” Applied Spectroscopy, 52 (11) 1472-1478, (1998).(PDF)