Issue 16, 2022

Stereoregular functionalized polysaccharides via cationic ring-opening polymerization of biomass-derived levoglucosan

Abstract

We report the facile synthesis and characterization of 1,6-α linked functional stereoregular polysaccharides from biomass-derived levoglucosan via cationic ring-opening polymerization (cROP). Levoglucosan is a bicyclic acetal with rich hydroxyl functionality, which can be synthetically modified to install a variety of pendant groups for tailored properties. We have employed biocompatible and recyclable metal triflate catalysts – scandium and bismuth triflate – for green cROP of levoglucosan derivatives, even at very low catalyst loadings of 0.5 mol%. Combined experimental and computational studies provided key kinetic, thermodynamic, and mechanistic insights into the cROP of these derivatives with metal triflates. Computational studies reveal that ring-opening of levoglucosan derivatives is preferred at the 1,6 anhydro linkage and cROP proceeds in a regio- and stereo-specific manner to form 1,6-α glycosidic linkages. DFT calculations also show that biocompatible metal triflates efficiently coordinate with levoglucosan derivatives as compared to the highly toxic PF5 used previously. Post-polymerization modification of levoglucosan-based polysaccharides is readily performed via UV-initiated thiol–ene click reactions. The reported levoglucosan based polymers exhibit good thermal stability (Td > 250 °C) and a wide glass transition temperature (Tg) window (<−150 °C to 32 °C) that is accessible with thioglycerol and lauryl mercaptan pendant groups. This work demonstrates the utility of levoglucosan as a renewably-derived scaffold, enabling facile access to tailored polysaccharides that could be important in many applications ranging from sustainable materials to biologically active polymers.

Graphical abstract: Stereoregular functionalized polysaccharides via cationic ring-opening polymerization of biomass-derived levoglucosan

Supplementary files

Article information

Article type
Edge Article
Submitted
09 jan 2022
Accepted
08 mrt 2022
First published
17 mrt 2022
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2022,13, 4512-4522

Stereoregular functionalized polysaccharides via cationic ring-opening polymerization of biomass-derived levoglucosan

M. K. Porwal, Y. Reddi, D. J. Saxon, C. J. Cramer, C. J. Ellison and T. M. Reineke, Chem. Sci., 2022, 13, 4512 DOI: 10.1039/D2SC00146B

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