The copolymerization of flexible poly(ethylene terephthalate)-poly(ethylene oxide terephthalate) poly(ether ester)s and brittle polylactic acid: Balanced mechanical properties and potential biodegradability

Abstract

The green sustainability of the plastic industry puts forward to unceasingly exploring new eco-friendly and adoptable polymers for meeting the requirement. Poly(ethylene terephthalate)-poly(ethylene oxide terephthalate) (PET-PEOT), one kind of poly(ether ester)s (PEEs) composed of soft PEOT segments and hard PET, is a nonbiodegradable polymer but shows attractive flexibility and ductility. Their distinctive properties are good complementary to biodegradable and brittle poly(lactic acid) (PLA). Therefore, in this study, PET-PEOT was copolymerized with PLA, and the effect of two copolymerization pathways (Pathway 1 and Pathway 2) on the chemical components and the sequence lengths of PET-PEOT and PLA segments in the resulting copolymers has been investigated in detail. It was found that the copolymers PET-PEOT-PLA fabricated via Pathway 2 of copolymerizing low molecular weight PET-PEOT with PLA by step-increasing temperatures are able to retain the average sequence lengths of PLA up to 16 in the resulting copolymers. Differential scanning calorimeter (DSC) and dynamic mechanical analysis (DMA) revealed that these copolymers PET-PEOT-PLAs had random segment distribution, and glass transition temperatures were monotonically decreased with increasing PET-PEOT contents. The initial decomposition temperatures of PET-PEOT-PLAs analyzed by thermogravimetric analysis were decreased with PLA content increasing. The mechanical properties and potential degradability of the copolymers have been significantly ameliorated.