Over the past two decades, biomass‐derived and biodegradable polylactide (PLA) has sparked tremendous attention as a sustainable alternative to traditional petroleum‐derived polymers for diverse applications. Unfortunately, the current applications of PLA have been mainly limited to biomedical and commodity fields, mostly because the poor heat resistance (resulting from low melting temperature) and hydrolysis stability make it hard to use as an engineering plastic. Stereocomplexation between enantiomeric poly(l‐lactide) (PLLA) and poly(d‐lactide) (PDLA) opens a new avenue toward PLA‐based engineering plastics with improved properties. The formation, crystal structure, properties, and potential applications of stereocomplex‐type PLA (SC‐PLA) are summarized by some research groups. However, since it is challenging to achieve full stereocomplexation from high‐molecular‐weight PLLA/PDLA blends and to avoid serious thermal degradation of the PLAs after complete melting, the advances and progress in the processing of SC‐PLA into useful products are quite rare in open publication. In this review, some important strategies for enhancing stereocomplex crystallization in practical processing operations are presented and recently developed processing technologies for SC‐PLA are highlighted, such as low‐temperature sintering. Furthermore, major challenges and future developments are briefly discussed. This review is expected to potentially open up new research activities in the processing of SC‐PLA.

Stereocomplexation of enantiomeric poly­(l-lactide)/poly­(d-lactide) (PLLA/PDLA) chains opens up a great opportunity toward sustainable PLA engineering plastic with exceptional heat resistance and durability. However, the processing and applications of stereocomplex-type PLA (SC-PLA) are significantly blocked by its inferior melt stability (i.e., the weak melt memory effect in triggering complete SC crystallization, which makes it hard to obtain exclusive formation of SC crystallites in melt-processed products) and inherent brittleness. In this contribution, we demonstrate an unprecedented strategy to address these obstacles by one-pot reactive melt blending of the equimolar PLLA/PDLA blend with reactive poly­(ethylene–methyl acrylate–glycidyl methacrylate) (E-MA-GMA) in the presence of catalyst, where both the stereocomplexation and the grafting of some PLLA/PDLA chains onto E-MA-GMA backbones take place simultaneously and competitively. Intriguingly, the E-MA-graft-PLA copolymer in situ formed can substantially improve the melt stability of SC-PLA matrix as compatibilizer, and thus highly crystalline SC-PLA/E-MA-GMA blend products with exclusive SC crystallites can be readily obtained by injection molding. Moreover, some E-MA-graft-PLA can also strengthen the blend interface as interfacial enhancer, which gives rise to an increase in the toughening efficiency. As a result, the obtained SC-PLA/E-MA-GMA blends exhibits impressive heat resistance (the Vicat softening temperature and heat deflection temperature are as high as 201 and 174 °C, respectively) and impact toughness (the notched Izod impact strength is close to 65 kJ/m2). Notably, their comprehensive performance is superior to some commercial petroleum-derived engineering plastics. Overall, the one-pot syntheses of copolymer by in situ grafting could open up a new horizon for creating super-robust SC-PLA-based engineering plastic using industrial melt-processing technologies.

Multi shape memory polymers (multi-SMPs) exhibit many potential applications such as aerospace, soft robotics, and biomedical devices because of their unique abilities. Although many works are done to broaden the preparations of multi-SMPs, the desire to a simple and versatile strategy as well as more complex shapes still exists. Moreover, a light-induced SMP shows more advantages than a thermal-induced one in many practical working circumstances. Herein, inspired by strong adhesion and efficient photothermal conversion of polydopamine (PDA) coating, we report a more simple and facile approach to prepare light-induced multi-SMPs by introducing a gradient PDA coating on a dual-SMP through time-controlled dipping. The photothermal converting properties with varying thicknesses of PDA under the tunable near-infrared light source are investigated. Then, light-induced multishape memory effects based on gradient PDA coatings are illustrated, where three designs of multi-SMPs - rectangle, triangle, and cross are prepared and demonstrated. Also, the evolutions of coating morphology during shape shifting are carefully studied. Finally, we present few complex designs of patterns and shapes as well as a design of potential application for the highly controllable smart devices. This strategy demonstrates a very simple and general strategy to design and prepare the light-induced multi-SMPs with complex shapes based on any thermal-responsive dual-SMPs.

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