(154y) Formation of PET Oligomers Via Microwave-Assisted Heating

This work investigates the formation of long-chain oligomers (LCO) as an alternative to the full glycolysis of PET. Heating for the reaction is done using microwave irradiation by taking advantage of the excellent microwave susceptor properties of the solvent, ethylene glycol. This enables rapid and selective heating of the solution and the potential for electrification through renewable energy sources. Mn oxide catalysts for depolymerization are investigated because Mn is a cheap and earth-abundant metal. Formation and characterization of the LCO are subsequently investigated. The molecular weights of the LCO change slightly based on the amount of solvent used but are much lower than the starting PET. As reaction time increases, the transesterification reaction proceeds to reduce the molecular weight and dispersion index of the oligomers. High surface area catalyst fully converted the PET to BHET (monomer) at 20 min at 220 °C. Oligomers had molecular weights of around 2000-3000 Da as determined by MALDI-TOF. Their flexibility was analyzed using NMR relaxometry and found to be comparable to PET. Thermal analysis demonstrated that the oligomers possess similar properties to PET. We discuss mechanistic insights into the formation of oligomers and monomers.