Biodegradable tough blends of poly(L-lactide) and poly(castor oil)–poly(L-lactide) copolymer

• Tensile toughness and elongation at break of PCO-g-PLLA copolymers are 10 and 30 times more than those of neat PLLA with minimal reduction in tensile strength of the PLLA matrix.
• Graft PLLA chains acted as a compatibilizer for the blending partner with PLLA matrix.
• Intermolecular interaction and interfacial adhesion were strengthened by entanglement and hydrogen bonding.
• PCO-g-PLLA particles of 0.1–3 μm and cross-linking of blends were favorable for toughness enhancement of PLLA.

PLLA grafted poly(castor oil) copolymers (PCO-g-PLLA) were successfully synthesized and used to enhance the tensile toughness of PLLA. The tensile toughness and elongation at break of the blends are 10 times greater and 30 times more than those of neat PLLA, respectively, with minimal reduction in the tensile strength of PLLA. Strong interfacial interaction between PLLA and PCO, homogeneous dispersion of the PCO rubbery particles in PLLA matrix, and the formation of cross-linking structure of PCO and PLLA were found to play important roles in the improvement of the toughness.