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Strengthened poly­(lactic acid) (PLA)-based materials with improved mechanical performance and improved thermal resistance, notably, are prepared by introducing stereocomplex crystallite (SC), an ideal filler, into the materials. Owing to the intermolecular hydrogen bond among the stereoisomer chains, the melting point of the special crystallite is up to 200 °C, which is 50 °C higher than the isostatic crystallite. The modulus of the PLA-based materials can be enhanced to several 100 MPa because of the integrated polymer chain arrangement. In this study, we electrospun hybrid nanofibers consisted of PLA stereoisomers and induced the stereocomplex crystallization under a mild condition (65 °C for 1 h). The mild warming is favorable for the protection of chlorogenic acid (CA) that was selected as the antibacterial agent. Both of Gram-positive and Gram-negative bacteria were efficiently cleared away using the warmed nanofibers that released CA rapidly within just a few hours. Used as filters, the SC electrospinning membrane also presented a potent filtering effect, leaving no bacteria retained in the filtrates. Attributing to SC, the PLA-based nanofibers showed extremely increased melting temperature over 200 °C and improved Young’s modulus up to 270.0 MPa. The durable nanofibers prepared in present study are meaningful for enlarging the application of PLA-based materials, for example, as filters, masks, and packages.

Poly­(lactic acid) (PLA) stereocomplex crystallite (SC)-based electrospun nanofibers were fabricated via annealing the as-spun membranes at 100 °C for 1 h. The heat-treated nanofibers exhibit enhanced mechanical properties and thermal resistance due to the existence of SCs, which restricts the lactide chain mobility. The formation of SCs increases the intermolecular forces between l-lactide and d-lactide segments, resulting in almost 2 times higher tensile strength (8.52 ± 0.29 MPa) and 3 times higher Young’s modulus (285.48 ± 1.19 MPa) than that of the untreated membranes, which is benefitting for wider applications. Additionally, a green absorbent named HTA synthesized from tannic acid and hexamethylenediamine was introduced into the nanofibers, giving the membrane richer functions. Based on the abundant reactive functional groups on the surface, small pore size and large surface area-to-volume ratio of the nanofibers, the HTA containing membranes exhibited excellent performance in adsorbing heavy metal ions and inhibiting bacterial growth. This bifunctional membrane showed reusability for 4 cycles with retaining good removal capability of Cr­(VI) and antibacterial effects. Furthermore, Cr­(VI) was found to be adsorbed and converted to less toxic Cr­(III) during the adsorption process, and bacteria, such as Escherichia coli and Staphylococcus aureus, were captured and broken on the surface of the nanofibers. In this study, we focused on a novel eco-friendly bifunctional SC-based PLA nanofiber to repeatedly adsorb metal ions and capture bacteria, and thus it is expected to have potential in various fields in the future.

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