Sustainable Approach for the Synthesis of Biopolycarbonates from Carbon Dioxide and Soybean Oil

A sustainable approach to produce biopolycarbonates was developed via copolymerizing carbon dioxide (CO2) and soybean oil-based terminal epoxide (SOTE) monomers in the presence of catalyst SalenCoCl and cocatalyst bis(triphenylphosphine)iminium chloride (PPNCl). The SOTE monomers were obtained through the synthesis of soybean oil with recycled epichlorohydrin which can be produced from crude glycerol, a byproduct of biodiesel production. The characteristic profiles of SOTE monomers and biopolycarbonates demonstrated a 100% conversion and a biopolycarbonate yield of 83.3%. It was also found that the original functional double bonds on the linear fatty acid chains were maintained in the biopolycarbonate products, which affords a functional basis for various promising applications. The highest biopolycarbonate yield was obtained at a CO2 pressure of 4 MPa; SOTE monomers of 0.01 mol; catalyst loading SalenCoCl and cocatalyst PPNCl of 0.04 mmol each, which was around 1.2% (w/w) based on the total weight of reactant; reaction time of 24 h; and reaction temperature of 22 degrees C. A transparent biopolycarbonate film with stable thermal properties was obtained. With the incorporation of SOTE monomers into the synthesis of propylene oxide and CO2, competitive biopolycarbonates were obtained with strong tensile strength and enhanced elongation. This innovative green synthesis route of incorporation of CO2 to soybean oil provides a sustainable platform for the production of biopolycarbonates from biobased feedstocks and CO2 for various applications.