Hierarchical crystallization strategy adaptive to 3-dimentional printing of polylactide matrix for complete stereo-complexation.

A novel strategy adaptive to 3D printing of PLA matrix for complete stereo-complexation was designed. Stereo-complexation has been demonstrated for its effectiveness in simultaneously improving aqueous stability and heat resistance of PLA. However, current techniques could not be directly incorporated into 3D printing of stereo-complexed PLA since stereo-complexed crystallites are easily formed before printing. High printing temperatures are thus required but decompose PLA materials at the same time. The hypothesis for this research is that controllable hierarchical crystallization in three thermal processes, the filament preparation, 3D printing and post annealing, could ensure feasibility of the strategy and a 100% stereo-complexation level in PLA matrices. Effects of extrusion, ambient and annealing temperatures on material structures were analyzed via WAXD, DSC and DMA. Resistance to hydrolysis and heat of the 3D printed PLA matrix was evaluated under practical conditions. It was showed that homo-crystallites anchored molecular chains of PLA during the post-annealing process for a high retention of tensile properties, while stereo-complexed crystallites provided stronger intermolecular interactions for improved hydrolytic and thermal resistance. This novel strategy via incorporating controlled hierarchical crystallization into 3D printing would enrich the fabrication and exploration of high-performance 3D printed PLA materials.