(648b) Lignin and CO2-Based Polymers

The fast expansion of the plastics industry has intensified the global crisis of plastic waste pollution, ecological imbalance, and greenhouse gas emissions. This presentation highlights the novel conversion method of greenhouse gas CO₂ with natural biomass lignin to develop new sustainable, recyclable polymers from abundant and non-food based renewable resources. A CO₂ and lignin-based cyclic carbonate monomer has synthesized using a cost-effective, non-phosgene-based and greener approach under atmospheric pressure and room temperature. The fully programable synthesis of CO₂ and lignin-based polymers is accomplished via ring opening polymerization (ROP) by varying the non-metallic organic catalyst loading (0.5 – 5.0 %) and reaction time (2 – 40 min). In the study, we have precisely determined the chemical structures of the synthesized cyclic carbonate monomers and polymers using various spectroscopic analyses including ¹H, ¹³C, and 2D HSQC NMR, FT-IR, and GPC. The high molecular weights (M_n: 120.34 – 154.58 kDa) and adequate thermal stabilities (T_d5%: 244 – 277 ºC from TGA and T_g: 33 – 52 ºC from DSC) of the polymers are advantageous for practical applications. Significantly, the CO₂ and lignin-based polymers have successfully recycled to the monomer for a circular plastic economy by adequate heating and reaction time in the presence of organic catalysts. This depolymerization process yields original structure of monomers that can be used for another polymerization without losing original chemical structures of the monomer and product polymers, making it a sustainable solution of end-of-life polymer waste. Therefore, this work illustrates an innovative hybrid approach of both the synthesis of 100% biomass-based polymer and closed-loop recycling of polymer-monomer using abundant renewable resources, that further leads to a sustainable circular plastic economy alternative to the linear petroleum-based polymers.