Preparation of stereocomplex powder from polycondensation poly(L-lactic acid) and poly(D-lactic acid) for use as a nucleating agent of high-molecular-weight poly(L-lactide)

High-molecular-weight poly(L-lactide) (HMW-PLLA), which is a biocompatible, biodegradable, and bio-based polymer, is an alternative to traditional petroleum-based plastics. However, its poor crystallizing ability limits its widespread application. In this paper, low-molecular-weight poly(L-lactic acid) (LMW-PLLA) and poly(D-lactic acid) (LMW-PDLA) synthesized through polycondensation of L-lactic acid and D-lactic acid, respectively, were used to prepare stereocomplex poly(lactic acid) (scPLA) powder using precipitation technique. Nucleation efficiency of the obtained scPLA powder was investigated by melt blending with the HMW-PLLA. The scPLA powder was nearly spherical in shape, had a single melting peak at 205 °C and exhibited complete stereocomplex crystallites. According to the differential scanning calorimetry (DSC) and X-ray diffractometry (XRD) analyses, the added scPLA powder improved the crystallization of HMW-PLLA and increased the crystallinity content of HMW-PLLA. Scanning electron microscopy (SEM) showed good phase compatibility between dispersed scPLA particles and HMW-PLLA matrices. The addition of scPLA powder had no significant effect on the tensile properties of the HMW-PLLA matrix. In conclusion, scPLA powder prepared from blending of polycondensation LMW-PLLA and LMW-PDLA showed a promising behavior to enhance the crystallized ability of HMW-PLLA.