Synthesis of Fully Biobased Polyesters from Plant Oil

Self-metathesis of fatty acid methyl esters (FAMEs) from natural oils and commercial oleic acid was carried out using a microwave reactor in solvent-free conditions. Self-metathesis products were further identified and quantified by gas chromatography–mass spectroscopy (GC–MS) and gas chromatography–flame ionization detector (GC–FID). Conversion of ∼50% was achieved within a short span (∼2 min) in the presence of 0.05 mol % Hoveyda–Grubbs second generation catalyst (HG2) giving an equilibrium mixture of alkenes, α,ω-diester, and FAMEs. Highly pure dimethyl-9-octadecene-1,18-dioate (diester) was separated, and the desired quantity of it was reduced to 9-octadecene-1,18-diol (diol). Condensation polymerization of diester and diol as monomers was performed using conventional heating, microwave irradiation, and microwaves coupled with conventional heating. Characterization and analysis of synthesized biopolyesters were carried out using different techniques including nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), thermal gravimetric analysis (TGA), dynamic mechanical analysis (DMA), and tensile tests. Polyesters with the highest molecular weight of 337 kDa, ∼50 °C melting point, degradation temperature of about 400 °C, and the maximum strength of ∼5.5 MPa were obtained. These materials have great future potential to be used in different applications as a substitute of nonrenewable polyesters.