Preferential formation of stereocomplex in high-molecular-weight polylactic acid racemic blend induced by carbon nanotubes

Stereocomplex (sc) crystallization is appealing to endow the poly(L-lactic acid)/poly(D-lactic acid) (PLLA/PDLA) blends with superior heat resistance. However, sc formation is dampened in the high-molecular-weight (HMW) racemic blends. Here, we disclosed a simple but effective approach to facilitate sc formation by introducing carbon nanotubes (CNTs) during the solution casting. As revealed by wide-angle X-ray diffraction and differential scanning calorimetry, the HMW equimolar PLLA/PDLA blends were overwhelmingly crystallized into sc modification in presence of a small amount of CNT, and the relative content of homocrystallites was notably decreased. Especially, exclusive formation of sc crystallites was found with only incorporation of 0.2 wt% CNTs. Such an intriguing phenomenon was probably attributed to the fact that CNTs acted as the anchor to promote intermolecular nexus and triggered the headmost crystallization between PLLA and PDLA. (C) 2016 Elsevier Ltd. All rights reserved.