Supertoughened poly(lactic acid) containing low content of poly(ethylene oxide) with balanced mechanical property: The role of mesophase and phase morphology

Poly(lactic acid) (PLA) inherently shows the distinct brittleness at room temperature, which is a major drawback limiting its practical applications. Great efforts have been done to improve the toughness by adding high content of flexible polymers or low content of nanoparticles, which is often at the expense of tensile strength. In this work, supertoughened PLA blend with high elongation at break (247.7%) containing low content of poly(ethylene oxide) (PEO) (8%) was directly fabricated by melt extrusion method. Interestingly, its tensile strength and modulus are only slightly decreased (<25%). The reasons for the balanced mechanical property can be understood as follows: I) The increasing mobility of amorphous chains of PLA due to the plasticizing effect of PEO. II) The strengthening effect of mesophase can hinder tensile strength to be severely sacrificed. III) The rod-like PEO phase can initiate more crazes and further prevents them from developing into cracks, allowing effective energy dissipation. This study proposes a facile but efficient strategy to fabricate PLA blends containing low content of PEO with balanced mechanical property, which would provide a clue for toughening other brittle thermoplastics.