Facile synthesis of polycarbonates from biomass-based eugenol: catalyst optimization for selective copolymerization of CO2 and eugenol to achieve polycarbonates

Abstract

In recent years, the quest for achieving polycarbonates in a sustainable, atom economical, and green manner has achieved significant momentum. Much focus has been given to epoxide monomers that are derived from renewable feedstocks. Renewable feedstocks are attractive green alternatives to established petroleum-based materials for reducing the dependency of the polymer industry on fossil resources. Herein, we have employed a series of Co and Cr(salen)-based complexes as selective catalysts for the copolymerization of CO₂ and eugenol epoxide. We have observed that varying both diamine backbone as well as the substituents on the phenolate rings of the salen ligand, thereby altering the electron density around the metal center, has notable effects on the reactivity and selectivity of polymer formation. It was also observed that a decrease in CO₂ pressure led to the formation of cyclic carbonates. Thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC) studies of the polymers reveal that these polymers are quite stable up to 250 °C and have relatively high glass transition (T_g) temperatures (83 °C). These findings present an easy strategy to prepare polycarbonates by using biobased eugenol monomers, and provide examples for potential sustainable polymer design and synthesis.