Nanostructured Phase Morphology of a Biobased Copolymer for Tough and UV-Resistant Polylactide

Despite technological feasibility and industrial scalability in toughening polylactide (PLA) by direct blending, avoiding the sacrifice of mechanical strength or full renewability remains a challenge. Here, low-molecular-weight poly(ethylene 2,5-furandicarboxylate)-block-polylactide (PEF-b-PLA) was synthesized to yield a fully biobased copolymer with expected partial miscibility with PLA. The ability of PEF-b-PLA to toughen PLA at 10 wt % (PLA10) and 20 wt % (PLA20) loadings was then evaluated. To understand the achieved properties, the formation of a nanostructured dispersion phase due to favorable interfacial adhesion arising from the miscibility of the PLA block with the PLA matrix was investigated. The morphological features, together with comparable strength inherited from the PEF blocks, afforded an unusual combination of toughness and strength for the PLA blends. Compared to the poor tensile toughness of a pure PLA film (1.77 MJ/m3), a striking increase of 839 and 912% was achieved for PLA10 and PLA20, respectively. More importantly, both pure PLA and the blends were characterized by comparable yield strength (∼30 MPa). This was accompanied by excellent UV-shielding imparted by the functional groups on the PEF blocks, which would improve the prospects of realizing PLA-based functional packing materials. The proposed design of copolymers, with good industrial feasibility, should be useful to guide the toughening approaches for PLA and probably other degradable polyester blends by profound morphology control.