Toughened PLA-b-PCL-b-PLA triblock copolymer based biomaterials: effect of self-assembled nanostructure and stereocomplexation on the mechanical properties

Abstract

The current research unfolds the effect of block lengths, microdomain morphology and stereocomplexation on the mechanical properties of PLA-b-PCL-b-PLA triblock copolymers where PCL is involved to improve the poor extensibility of PLA. The linear triblock copolymers PLLA-b-PCL-b-PLLA and PDLA-b-PCL-b-PDLA (PLLA:poly (L-lactic acid) and PDLA:poly (D-lactic acid)) are made by two step ring opening polymerization and blended in a 1 : 1 ratio to achieve stereocomplex blends where the molecular weight of the terminal and the mid segment is tailored. The mechanical strength and elongation at break range from 13 MPa to 36 MPa and 540 to 950%, respectively, for the triblock copolymers with varied block lengths. Such wide-ranged mechanical properties are ascribed to the morphology of the self-assembled nanostructure of triblock copolymers as corroborated with the small angle X-ray scattering (SAXS) results. To render it industrially viable, the process of triblock copolymer synthesis is scaled up to ∼500 g batch followed by its processing using a twin-screw extruder to make a filament which is used for 3D printing of a mesh-type scaffold. The synthesized materials are tested for their biocompatibility by performing MTT assay using rat bone osteosarcoma (UMR-106) cells which renders them as potential biomaterials.