Manipulating Matrix Crystallization and Impact Toughness of Polylactide/Elastomer Blends via Tailoring Size and Packing Density of Stereocomplex Crystallites Formed at the Interface

Abstract

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.

Super Toughened PLLA/PBAT Blends with Modified Phase Interface via Constructing Cocontinuous Structure with the Aid of Stereocomplex Crystallites Toward Preparation of a Fully Degradable Material

“…The pristine PLLA/PBAT blend presented a typical "sea−island" morphology, and some cavitations caused by the interfacial debonding of PBAT phases were observed due to the poor interfacial adhesion between PLLA and PBAT. 34,35 With the addition of PBAT-g-GMA (Figure 6b), the blend of L/B/P also displayed interfacial cavitation, whereas the interfaces became vague with the decreased size of PBAT particles, suggesting a slight improvement in compatibility. However, an increased plastic deformation with fibers and cavitations were observed as the content of PDLA increased.…”