Plasmaoxidative and Chemical Degradation of Poly(ethylene terephthalate) Studied by Matrix-assisted Laser Desorption/Ionization Mass Spectrometry

Abstract

A model system of linear ethylene glycol terminated poly(ethylene terephthalate) oligomers of the general formula H–[GT]n–G (where G is an ethylene glycol unit and T represents a terephthalic acid unit) was synthesized and exposed to an oxygen plasma. The degradation of the oligomers was investigated by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The results were compared to a chemical degradation of commercial poly(ethylene terephthalate) which had been exposed to an aqueous solution of natural chalk for many years. In both cases an ester scission process was found which generates terephthalic acid terminated oligomers (H–[GT]m–OH) and decomposes linear ethylene glycol terminated oligomers (H–[GT]m–G). The scision of the ester bonds during the chemical treatment additionally leads to the formation of T–[GT]m–OH like oligomers and to a strong decrease of the number of cyclic oligomers ([GT]m). Furthermore during the plasma treatment an additional formation of [GT]m–G like cyclic oligomers was observed.