Gateway to Sustainable Polymers via Catalytic ROCOP of CO ₂ /COS Utilizing a Renewable Epoxide Monomer from Furfural Derivatives

In recent years, there has been an increase in demand for a paradigm shift from fossil fuel-based feedstock to renewable feedstock for polymer synthesis due to the need for expanding the source of these materials as well as enhancing their (bio)-degradability. Lignocellulosic biomass can serve as a promising renewable feedstock that can be converted to platform chemicals. Furfural is one of the crucial platform chemicals that is derived from xylan-rich lignocellulosic biomass. Furfural is an excellent molecular platform that can open a gateway to a diverse range of furan-based epoxide monomers. Herein, we report a furan-based epoxide monomer synthesized by using two furfural derivatives (furoyl chloride and furoic acid). The epoxide has been screened for catalytic ring-opening copolymerization (ROCOP) with carbon dioxide (CO₂) and carbonyl sulfide (COS) employing binary catalysts comprising Co-salen and Cr-salen complexes, respectively, in conjugation with phosphonium salts. The polycarbonates and poly-(monothiocarbonates) showed thermal stability up to 150 °C with <i>T</i> _gs of 58.6 and 49.2 °C, respectively. The aliphatic polycarbonate exhibited hydrolytic degradability under basic conditions to produce diol. The diol generated by the degradation of polycarbonate was recycled back to epoxide monomer through tosylation reaction, followed by ring-closing of the tosylated product. The mechanical properties of the polymer sample were accessed by performing a lap shear test and nanoindentation testing. The lap shear test revealed that the polycarbonate sample exhibited better adhesive performance than poly-(monothiocarbonates), while nanoindentation testing showed poly-(monothiocarbonates) exhibited higher hardness and elastic modulus than polycarbonates.