Fabrication, structure, and properties of Poly-(Lactide) multilayers with ultrahigh content, ordered, and continuous transcrystallinity

Abstract

Transcrystallinity (TC) as a classic type of crystals has abstracted increasing attention due to its peculiar morphology and impacts the properties of materials in many aspects. Nevertheless, owing to the low content, disorder, and discontinuity of TC achieved by conventional methods, its formation mechanism and growth law still unclear, and its impact on the properties remains debatable. Here a strategy is proposed to construct all PLA-based multilayers composed almost entirely of the TC. PLLA and PDLA are coextruded to form the alternating multilayers, in which the PLLA and PDLA diffuse each other and thus form the two-dimensional stereocomplex (2D-SC) at the multilayered interface, subsequently, the 2D-SC induce the TC growing into the whole layer space. The POM, SEM, and 2D-WAXD results reveal that the TC is composed of highly compact and oriented lamellae, whose b-axis lays perpendicular to, but the a-axis and c-axis parallel to the multilayered interface. Such oriented morphology of TC does impact the properties of PLA. Not limited to the PLA, the strategy proposed here can also be applied to other two complementing stereoregular polymers, where the stereoselective interaction induces the formation of polymer SC. So, this effort could be a useful reference to the research on polymer TC.