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Constructing stereocomplex (SC) crystallites at the interface of poly(L‐lactide) (PLLA)/elastomer blends represent a promising strategy to develop heat‐resistant and super‐tough PLLA materials because such SC crystallites can behave as not only nucleator to accelerate crystallization of PLLA matrix but also interfacial binder to strengthen interface. The properties of blends could be largely dominated by the SC interfacial layer, however, it is still unclear how the interfacial structure affects nucleating efficiency and interfacial strength. Herein, taking PLLA/poly(ethylene‐co‐methyl acrylate‐graft‐poly(D‐lactide)) (EMA‐g‐PDLA) blends as an example, EMA‐g‐PDLA bearing different chain lengths and grafting densities is prepared to tailor the size and packing density of interface‐localized SC crystallites. The results indicate that the interfacial structure and properties of the blends have been successfully manipulated. Compared with low‐graft‐density long PDLA chains, high‐graft‐density short ones can readily collaborate with PLLA chains to form numerous SC crystallites with smaller size and higher packing density at the interface and thus dramatically enhance the impact toughness and matrix crystallization rate. Moreover, the toughness is dominated by the content of SC crystallites, but the matrix crystallization is determined by their size and packing density. The work provides a new understanding of SC structure controlling the properties of PLLA/elastomer blends. [ABSTRACT FROM AUTHOR]

Stereocomplex (SC) crystallization can prominently improve the physico-chemical properties of poly(l -lactide)/poly(d -lactide) (PLLA/PDLA) blends, yielding a novel polylactide (PLA) material. However, the predominant formation of SC crystals in the melt-processing of high-molar-mass (high-MW, >100 kg/mol) enantiomeric PLA blends remains a huge challenge due to the competition between SC crystallization and homocrystallization. Herein, double-grafted copolymer having both PLLA and PDLA side chain has been designed and synthesized as an efficient crystallization promoter for the harvest of SC crystals in the high-MW PLLA/PDLA blends. The results show that, with the addition of such a copolymer, the blends can preferentially crystallize into SC crystals in both isothermal and non-isothermal conditions. Promisingly, the SC crystals can be exclusively formed by adding only small amounts (e.g., 0.5 wt%) of the copolymer, without the formation of any homocrystals. This interesting observation can be interpreted by the crucial role of the unique copolymer in suppressing the phase separation of the opposite PLA enantiomers upon melting as an efficient compatibilizer and then encouraging the generation of alternatingly arranged PLLA/PDLA chain clusters favored for SC nucleation and crystal growth. These findings provide new inspiration for the development of high-performance PLA with desirable SC crystallizability. [Display omitted] [ABSTRACT FROM AUTHOR]

Stereocomplex-type polylactide (SC-PLA) has recently emerged as an up-and-coming engineering Bio-plastic because the SC crystallization between enantiomeric poly(l -lactide) (PLLA) and poly(d -lactide) (PDLA) can substantially enhance the heat resistance and hydrolytic stability. Unfortunately, it is exceedingly challenging for high-molecular-weight PLLA/PDLA blends to preferentially crystallize into SC crystals (SCs) during melt processing and the concomitant formation of homocrystals (HCs) causes a significant deterioration in physio-chemical properties of final products. Herein, a dibenzoylhydrazide compound has been utilized as an efficient nucleating agent (NA) for the SC crystallization of PLLA/PDLA blends. The results indicate that, in both non-isothermal and isothermal crystallizations, the SC crystallization is markedly promoted with the incorporation of 0.2–1.5 wt% NA. Specially, the enantiomeric blends with relatively high amounts (≥0.5 wt%) of NA are found to exclusively crystallize into SCs without any HCs formation. Meanwhile, the NA can accelerate the SC crystallization and reduce the crystal size. The preferential SC crystallization should be associated with the hydrogen-bonding interactions between PLAs and NA molecules, which could lower barriers for the nucleation and crystal growth of SCs. Our work provides a facile yet powerful strategy for the preparation of high-performance SC-PLA materials with exceptional SC crystallization ability. [Display omitted] • TMC can act as an efficient NA to promote the SC crystallization of PLLA/PDLA blends. • Exclusive formation of SCs is achieved after adding 0.5 wt% TMC into the blends. • The crystallization is greatly accelerated due to the increase in nucleation density. • The hydrogen bonding between TMC and PLA is responsible for the enhanced SC formation. • A facile strategy has been proved to develop SC-PLA with exceptional crystallizability. [ABSTRACT FROM AUTHOR]