Elucidation of Substantial Differences in Ring-Opening Polymerization Outcomes from Subtle Variation of Glucose Carbonate-Based Monomer Substitution Patterns and Substituent Types

Abstract

The substituents present upon five-membered bicyclic glucose carbonate monomers were found to greatly affect the reactivities and regioselectivities during ring-opening polymerization (ROP), which contrast in significant and interesting ways from previous studies on similar systems, while also leading to predictable effects on the thermal properties of the resulting polycarbonates. Polymerization behaviors were probed for a series of five fivemembered bicyclic 2,3-glucose-carbonate monomers having 4,6-ether, -carbonate, or -sulfonyl urethane protecting groups, under catalysis with three different organobase catalysts. Irrespective of the organobase catalyst employed, regioregular polycarbonates were obtained via ROP of monomers with ether substituents, while the backbone connectivities of polymers derived from monomers with carbonate protecting groups suffered transcarbonylation reactions, resulting in irregular backbone connectivities and broad molar mass distributions. The sulfonyl urethane-protected monomers were unable to undergo organobase-catalyzed ROP, possibly due to the acidity of the proton in urethane functionality. The thermal behaviors of polycarbonates with ether and carbonate pendant groups were investigated in terms of thermal stability and glass transition temperature (T g ). A two-stage thermal decomposition was observed when tert-butyloxycarbonyl (BOC) groups were employed as protecting side chains, while all other polycarbonates presented high thermal stabilities with a single-stage thermal degradation. T g was greatly affected by side-chain bulkiness, with values ranging from 39 to 139 °C. These fundamental findings of glucose-based polycarbonates may facilitate the development of nextgeneration sustainable highly functional materials.

Quantitative, Regiospecific, and Stereoselective Radical Ring-Opening Polymerization of Monosaccharide Cyclic Ketene Acetals

“…Inspired by the structures and properties of biopolymers, chemists have sought to construct degradable polymers by using biologically derived building blocks. In particular, carbohydrates have been considered a promising feedstock for polymer synthesis because of their natural abundance and unique material properties. − For example, carbohydrate polymers and native polysaccharides have been generated via anionic and cationic polymerizations. − Despite progress in the ionic polymerization of carbohydrate-derived monomers, radical polymerization, which is widely used to synthesize vinyl polymers and has demonstrated good functional group tolerance, remains underutilized for producing carbohydrate-based degradable polymers.…”