Green Insights into Levoglucosenone Polyesters: ADMET Polymerization vs Metal- and Enzyme-Catalyzed Polycondensation

This study investigates the synthesis of α,ω-dienes derived from levoglucosenone (LGO) and their polymerization via Acyclic Diene Metathesis (ADMET) polymerization, with a focus on sustainability and efficiency. The monomers were prepared using two approaches: Steglich and lipase-catalyzed esterification. While the chemical method achieved higher yields, the enzymatic route provided a more environmentally friendly alternative. ADMET polymerization was then applied for the first time to LGO-derived monomers using six different ruthenium-based catalysts, leading to high conversion rates and LGO-based polyesters with molecular weights (Mn) of up to 6 kDa. Thermal analysis showed glass-transition temperatures (Tg) ranging from −39 to −7 °C, depending on the monomer, while thermogravimetric analysis (TGA) demonstrated Td5% above 300 °C. To assess the environmental impact of different polymerization methods reported to produce LGO polyesters, this study also benchmarked the results against polyesters from (1R,2S,4S,5R)-6,8-dioxabicyclo[3.2.1]octane-2,4-diol (HO-LGOL)─the precursor to the α,ω-dienes─using both metal- and enzyme-catalyzed polycondensations. Among all the methods tested, solvent-free ADMET polymerization showed the lowest E-factors (0.019–0.026 kg waste/kg polymer), whereas solution-based ADMET and enzymatic polymerization generated significantly more waste due to solvent consumption. Metal-catalyzed polycondensation resulted in moderate waste levels but required higher temperatures (160–220 °C), leading to increased energy consumption. The qualitative analysis of energy efficiency further highlighted ADMET polymerization as a greener approach, requiring only 30 min at 80 °C, in contrast to the longer reaction times needed for metal- and enzyme-catalyzed polymerizations. Overall, this study demonstrates that ADMET polymerization offers a promising and greener route for polyester synthesis from levoglucosenone, balancing reaction efficiency, environmental impact, and polymer properties.