Mechanical Toughening of Telechelic Copolymer to Poly(lactic acid) Blends: Perspectives of Microstructural Comparison and Molecular Simulation

Poly(lactic acid) (PLA) is a renewable polyester material with excellent properties, such as processability, biocompatibility, and biodegradability, and is widely used in packaging and medical applications. However, neat PLA has the performance limitations of high brittleness and poor toughness, strongly restricting its practical use. In this study, three poly(ethylene glycol) (PEG)-based telechelic polymers were synthesized with different microstructures: linear epoxidized poly(ethylene glycol) (linear EPEG), 4-arm star-shaped epoxidized poly(ethylene glycol) (4A-EPEG), and 4-arm star-shaped poly(lactic acid-glycolic acid)-epoxidized polyethylene glycol (4A-PLGA-EPEG). These telechelic polymers that take the reactive epoxy groups on the terminals of the chains endowed the reactive compounding with the PLA matrix to achieve the mechanical enhancement of the blends. At a low loading level (3 wt%), the introduction of 4A-PLGA-EPEG significantly improved the toughness of the PLA-based blends with a substantial increase in elongation at break of 107.43% compared to only 3.84% for the neat PLA material. In contrast to linear EPEG and 4A-EPEG, the 4A-PLGA-EPEG copolymer served as a mechanical toughening agent because of its enhanced compatibility and the formation of topological entanglements with the polymeric matrix in the blends. The calculation of the efficiency factor ( η ) quantified the improvement in the microstructure stability and stress transfer efficiency of blends derived from the chain entanglements of the added copolymer, and molecular simulations further confirmed the formation of a micro-topological structure by reactive compounding in PLA-based blends.