Exclusive formation of poly(lactide) stereocomplexes with enhanced melt stability via regenerated cellulose assisted Pickering emulsion approach

Stereocomplexation of enantiomeric poly(L-lactide)/poly(D-lactide) (PLLA/PDLA) endows the Polylactide (PLA) with outstanding heat resistance and durability. However, PLA with exclusive stereo-complexation (sc-PLA) is difficult to achieve. Both stereo-complexation PLA and homo-crystallization PLA (hc-PLA) often formed together when PLLA and PDLA blended. In this research, a new strategy was proposed to prepare the PLA with exclusive stereo-complexation (without homo-crystallization) by Pickering emulsion approach, where regenerated cellu-lose (RC) was used to stabilize the PLLA/PDLA blends and form RC/sc-PLA microsphere. The DSC result shows that the PLA composites prepared in this method presents single melt peak around 220 C, which is the char-acteristics of sc-PLA. Most important, this 0.5%RC/sc-PLA possesses excellent melt stability. It does not divide into stereo-complexation and homo-crystallization during the 3 heating cycles. The results indicate that Pick-ering emulsion approach firstly provide the limited space to limit the diffusion of macromolecular chains and fully combine PLLA and PDLA chains and form complete RC/sc-PLA microspheres. Then the microspheres were hot pressed into films and homogeneous distribution of RC as heterogeneous nucleation agent provides nucle-ation sites. The intermolecular hydrogen bonding between RC and PLA improves crystallization property and stabilizes the stereo-complexation. This study provides a strategy to prepare the PLA materials with exclusive stereo-complexed crystal and excellent melt stability, which determines the heat resistance and repeated processing.

Automated summary

A new method using Pickering emulsion approach was proposed to prepare PLA with exclusive stereo-complexation. Regenerated cellulose (RC) was used to stabilize PLLA/PDLA blends and form RC/sc-PLA microspheres. The PLA composites prepared in this method showed excellent melt stability.